The phrase is hence why grammatically correct asks a useful question about modern English usage and clarity. Writers often wonder whether hence can sit next to words like is and why without creating a grammar problem, and that confusion is understandable. In the sentence “This is hence why we need a rule,” this is a pronoun (subject), is is a linking verb in the present tense, hence is an adverb, why is a subordinating conjunction or interrogative adverb depending on use, we is a pronoun (subject of the clause), need is a verb (present), a is an article, and rule is a noun; the sentence mixes functions in a way many editors find awkward.
In this article I identify parts of speech (nouns, verbs, adjectives, adverbs, prepositions, conjunctions, pronouns), check verb tenses and subject–verb agreement, and review articles, prepositions, and modifiers for precision so you can decide if is hence why works for your sentence.
You will see clear contextual examples, common mistakes to avoid, notes on American vs British English tendencies, idiomatic expressions, and practical tips to make your writing clean and grammatically correct. Read on to learn how to use hence correctly and where other constructions are better.
Contextual Examples
Simple Declarative Use: Avoiding Awkward Stacking
1: “That is why we left.”
- Parts of speech: That (pronoun subject), is (linking verb), why (conjunction/adverb), we (pronoun subject of subordinate clause), left (verb, past).
- Verb check: is agrees with singular subject That; left is past tense and agrees with plural subject we. This sentence is clear and idiomatic. Note that why introduces a clause giving the reason, and no extra adverb is needed.
2: “That is hence the reason we left.”
- Parts of speech: That (pronoun), is (verb), hence (adverb), the (article), reason (noun), we (pronoun), left (verb, past).
- Verb check: is matches That. Here hence modifies the noun phrase the reason; it works but feels slightly formal or stilted.
3: “That is hence why we left.”
- Parts of speech: That (pronoun), is (verb), hence (adverb), why (conjunction/adverb), we (pronoun), left (verb, past).
- Analysis: This mixes hence and why in succession. Grammatically, it is not strictly impossible, but it is clumsy because hence and why both play roles that express reason. Style guides generally prefer one clear connector: “That is why we left.” or “That is hence the reason we left.”
Present Perfect and Perfective Uses
Sentence: “It has therefore become clear why we act.”
- Parts of speech: It (pronoun subject), has become (present perfect verb phrase), therefore (adverb), clear (adjective), why (subordinating conjunction), we (pronoun), act (verb).
- Verb check: has become correctly matches singular subject It. Therefore modifies the clause has become clear. This is a smooth, formal way to link cause and effect.
Sentence: “The study is hence why these policies were adopted.”
- Parts of speech: The study (noun phrase), is (linking verb), hence (adverb), why (conjunction), these policies (noun phrase), were adopted (passive verb, past).
- Analysis: This sentence is awkward. A clearer version: “The study is the reason why these policies were adopted.” or “Hence, the study explains why these policies were adopted.”
Using Hence at Sentence Start for Clarity
Sentence: “Hence, we revised the plan.”
- Parts of speech: Hence (adverb), we (pronoun subject), revised (verb, past), the (article), plan (noun).
- Verb check: revised agrees with plural subject we. Starting a sentence with Hence, is formal but grammatically correct. It cleanly signals consequence or result.
Sentence: “We revised the plan, hence the delay.”
- Parts of speech: We (pronoun), revised (verb), the (article), plan (noun), hence (adverb), the (article), delay (noun).
- Verb check: revised is past; sentence fragments can be stylistic here, but editors may prefer “We revised the plan; hence, there was a delay.”
Combining Hence With Other Connectors Carefully
Sentence: “He failed to appear; hence, the trial was postponed.”
- Parts of speech: He (pronoun), failed (verb, past), to appear (infinitive), hence (adverb), the trial (noun phrase), was postponed (passive verb phrase).
- Verb check: Verbs agree with their subjects. This structure—two clauses linked by hence—is formal and correct.
Sentence: “That is why, hence, we proceed cautiously.”
- Analysis: Multiple connectors why and hence close together create redundancy. Prefer one connector or reorder: “That is why we proceed cautiously” or “Hence, we proceed cautiously.”
Common Mistakes
Mistake 1: Stacking Connectors (Is Hence Why)
Error: “This is hence why we must act.”
- Why wrong: hence and why both signal reason. Using them together creates redundancy and awkward flow.
- Correction: “This is why we must act.” or “Hence, we must act.”
- Parts-of-speech check: In the corrected sentences, pronouns, verbs, and conjunctions align cleanly; no redundant connectors remain.
Mistake 2: Using Hence Informally in Speech
Issue: hence is formal and fits written, formal, or academic registers. Saying “hence” in casual speech can sound stilted. Use “so” or “therefore” in informal contexts.
- Example: Casual: “So we left early.” Formal: “Hence, we left early.”
Mistake 3: Misplacing Hence Within Clause
Error: “They hence decided to postpone the meeting.”
- Why awkward: While this is not strictly ungrammatical, placing hence between subject and verb is less natural. Better placements: “Hence, they decided to postpone the meeting.” or “They decided to postpone the meeting; hence, the delay.”
Mistake 4: Confusing Hence With Therefore/Thus
Error: “He was late; therefore why did he apologize?”
- Why wrong: Combining therefore and why is redundant when both introduce cause or reason.
- Correction: “He was late; therefore, he apologized.” or “Why did he apologize? Because he was late.” Choose one structure per clause for clarity.
Mistake 5: Using Hence With Explicit Past Time Markers Incorrectly
Error: “He hence went yesterday.”
- Why awkward: hence signals consequence, not a sequence in time. Use so or therefore and place time markers clearly: “He went yesterday; hence, we met earlier.” or “He went yesterday, so we rescheduled.”
American vs British English Differences
Usage and Register
Both American and British English accept hence as a formal connector meaning “for this reason” or “consequently.” The main difference lies in register preferences: British English writers may use hence slightly more in formal prose, but the difference is small. In both varieties, hence is best suited to written and formal contexts.
Placement and Punctuation
- Americans often prefer “Therefore, …” or “So, …” in everyday writing. Hence remains acceptable in academic and legal texts.
- British academic writing may use hence without issue. Both varieties recommend using hence at the beginning of a clause or sentence, or after a semicolon: “He was late; hence, the delay.”
Colloquial Alternatives
- American informal: so, therefore, as a result
- British informal: so, therefore, as a result
- For both: choose the less formal word for speech and the more formal word (hence, therefore) for essays and reports.
Idiomatic Expressions
Hence in Set Phrases
- “Hence the conclusion” — used to point to a result. Example: “The data were incomplete; hence the conclusion that further tests are required.”
Parts of speech: The data (noun phrase), were (verb), incomplete (adjective), hence (adverb), the conclusion (noun phrase). Verb check: were agrees with plural data. - “From henceforth” — archaic phrase meaning from now on; modern writing prefers henceforth without from or simply from now on.
Example (modern): “Henceforth, members must register.”
Why vs Hence: Idiomatic Choices
- “This is why” is idiomatic and conversational. Example: “This is why we train.”
- “Hence” is idiomatic in formal cause-and-effect statements. Example: “The error persisted; hence, the system failed.”
- Avoid combining them. Use one strong connector for readability.
Combining with Other Connectors Carefully
- “Therefore hence” — wrong and redundant. Use “therefore” or “hence.”
- “Hence why” — redundant; prefer “hence” or “why” alone depending on structure.
Practical Tips
Tip 1: Prefer One Connector Per Clause
If a clause already contains why as a subordinating conjunction, do not add hence immediately after the verb. Example: “That is why we left” is better than “That is hence why we left.”
Tip 2: Use Hence at Clause Start or After Semicolon
Good structures:
- “Hence, we must revise the plan.”
- “We revised the plan; hence, the delay.”
Both are formal and clear.
Tip 3: Choose Tone-Appropriate Words
- Formal writing: hence, therefore, thus.
- Informal writing: so, therefore, because of that.
Match the tone to your audience to avoid sounding stilted.
Tip 4: Check Parts of Speech When Rewriting
When you rewrite a sentence, label parts of speech quickly: subject (noun/pronoun), verb (tense and agreement), connectors (conjunctions, adverbs). This reveals misplaced adverbs or redundant connectors.
Tip 5: Avoid Redundancy
If a sentence already includes because, since, or why, do not add hence as well. One clear reason marker is enough.
Tip 6: Read Aloud for Flow
Reading a sentence aloud often reveals clumsy clusters such as “is hence why.” If the sentence trips your tongue, simplify it.
Tip 7: Use Punctuation to Separate Connectors
If you choose to use hence mid-sentence, set it off with commas or a semicolon for clarity: “The team missed the target; hence, we revised our budget.”
Tip 8: When in Doubt, Restructure
If is hence why looks awkward, try: “This is why we …” or “Hence, we …” or “Therefore, we …” Each variant clarifies the relation without stacking connectors.
Tip 9: Teach with Minimal Pairs
Show learners pairs to practice:
- “He left because he was tired.”
- “He was tired; hence, he left.”
- “He left because he was tired; therefore, he did not drive.”
Comparing shows how connectors change rhythm and formality.
Tip 10: Consult Usage Guides for Formal Contexts
If writing legal, academic, or technical prose, consult a style guide (Chicago, APA, MHRA) for preferred connector usage and punctuation. These guides often recommend hence for formal consequences but caution against redundancy.
Conclusion
The sequence is hence why is not strictly ungrammatical, but it is stylistically redundant and often awkward. Both hence and why mark reasons; using both together usually doubles up on the same function. For clarity and smooth flow prefer one connector: “That is why…” or “Hence,…” or “Therefore,…” When you do use hence, place it at the start of a clause or after a semicolon and check verb tense and subject–verb agreement. Label parts of speech when editing to spot misplaced modifiers and redundant connectors. Apply the practical tips here to write clearly in both American and British contexts, matching tone and audience.
FAQs
- Q: Is “is hence why” grammatically correct?
A: It is not strictly ungrammatical, but it is stylistically redundant and awkward because hence and why both mark reason. Prefer “That is why…” or “Hence,…” for clarity. - Q: Can I use “hence” and “why” in the same sentence if I reorder?
A: Yes, carefully. For example: “Hence the reason why we left is clear.” But this still feels heavy. Better: “Hence the reason we left is clear” or “This is why we left.” - Q: Where should “hence” be placed in a sentence?
A: Place hence at the start of a clause or after a semicolon: “He failed the test; hence, he retook the course.” Avoid inserting hence directly between is and why. - Q: Is “hence” more formal than “so”?
A: Yes. Hence is more formal and suits academic or formal writing. Use so in casual speech and informal writing. - Q: Does American English prefer “hence” less than British English?
A: Slightly—both varieties accept hence in formal contexts. In casual American English, hence is rarer. Choose based on audience and tone. - Q: Can “hence” substitute for “therefore”?
A: Often yes. Both mean as a result. Therefore is common in academic writing; hence is more concise and formal. - Q: Is “is hence why” acceptable in speech?
A: It may be heard in speech, but it sounds clumsy. Speakers usually prefer “that’s why” or “so” in conversation. - Q: How do I edit a sentence with “is hence why”?
A: Pick one connector: rewrite as “That is why…” or “Hence, we…” or “Therefore, …” Ensure verb tense matches any time markers.
