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hence

/hens//hens/·adverb
for this reason, therefore; also: from this time or place
Fig. 1 — A ball drops onto a ramp and rolls down under nothing but its own weight, gathering pace, until it clips a small switch at the bottom.
01Definition

Hence is a compact, formal way of saying 'for this reason, it follows that'. It draws a line from a cause you have just stated to the conclusion that flows out of it, which is why it likes to sit between a fact and its consequence. Older, more literal senses survive too — 'a week hence' means a week from now, 'get hence' means away from here — but in academic prose it is almost always the logical 'therefore'. Unlike 'because', it points forward to the result rather than back to the cause.

02In use
  • iThe samples were contaminated; hence, the results cannot be trusted.
  • iiThe bridge was built in 1890 and hence predates every other structure in the survey.
  • iiiThe readings rose only at dawn; hence we can infer that sunlight drives the reaction, and the original hypothesis still holds.
03Collocations
  • hence the name
  • hence the need for
  • a few years hence
  • hence it follows that
  • hence the delay

Family henceforth (adverb) · henceforward (adverb)

04Relations

=therefore, thus, consequently, accordingly, so

06TOEFL & IELTS

A clean, formal connector that lifts Writing above 'so'. Two patterns: as a sentence adverb with a comma ('…contaminated; hence, the results…'), or fronting a verbless noun phrase ('hence the delay', 'hence the need for caution'). Don't follow it with 'that'. Use it sparingly — one or two per essay reads as control, more reads as a tic.

07Asked
What is the difference between hence, thus, and therefore?
All three draw a conclusion, with slight leanings. Therefore is the plain, all-purpose 'for that reason'. Thus leans toward 'in this way', often summarising a method or result. Hence is the most compact and formal, pointing forward from a cause to what follows — the visible glowing bulb at the end of the chain in the scene above. In most sentences they are interchangeable.
Is 'hence why' grammatically correct?
It is widely considered redundant. Hence already means 'for this reason', so 'hence why' says 'for this reason why' — the 'why' repeats what 'hence' has covered. Careful writing uses either 'hence the delay' or 'which is why the delay', not 'hence why the delay'. It is common in speech, but exams and formal prose penalise it.
What does 'a week hence' mean?
A week from now — 'hence' in its older, temporal sense of 'from this time forward'. 'Two years hence' means two years in the future. This use is formal and a little archaic, but still appears in legal and literary writing. It is a separate sense from the logical 'therefore', so context tells you which is meant.
What is the difference between henceforth and henceforward?
Almost none — both mean 'from now on', and both are formal. 'Henceforth, all visitors must sign in.' Henceforth is the more common of the two; henceforward is slightly older and heavier. Either sets a rule or state beginning now and continuing. Note the sense: these look forward in time, like 'a week hence', not backward to a cause.
Can you start a sentence with 'hence'?
Yes. Two patterns work. As a sentence adverb it takes a comma — 'The samples were contaminated; hence, the results were discarded.' Or it can front a verbless phrase with no comma — 'Hence the delay', 'Hence the need for caution'. What it does not take is a following 'that' — write 'hence the confusion', never 'hence that'.
Is 'hence' too formal for essays?
No — it is a clean, formal connector that lifts writing above 'so', and it is well suited to IELTS and TOEFL Task 2. The only caution is dosage: one or two uses per essay read as controlled and precise; more start to read as a verbal tic. Vary it with 'therefore' and 'as a result' to keep the prose natural.