Past Tense of “sink”

The past tense of sink is sank; the past participle is sunk.

Why “sink” behaves this way

"Sink" comes from Old English "sincan," another class-3 strong verb following the same i/a/u vowel pattern as "sing" and "drink." The noun "sink" (a basin for washing) is a much later development, first used in English only a few centuries ago to describe a fixture that water drains, or sinks, into.

"Sunk" has also become an accepted alternative simple past in informal speech ("the ship sunk fast"), a genuine and long-standing variation rather than a recent error, though "sank" remains the preferred form in careful written English while "sunk" is reserved there strictly for the participle.

The common confusion

The real confusion mirrors its close relatives: "sunk" used as a bare simple past ("the ship sunk") is widespread in casual speech and is gradually gaining ground even in edited writing, while the reverse error, "sank" after a helping verb ("has sank"), is somewhat less common but still frequent. 'Sink' and 'sank' also appear in the specifically nautical register of shipwreck reporting, where formal maritime English still strongly prefers 'sank' for the simple past even as casual speech increasingly accepts 'sunk' in that same slot, a genuine ongoing shift rather than a settled rule.

How it's actually used

"Sink" extends into figurative territory readily — "sinking feeling," "sink into depression," "sink or swim" — and the adjective "sunken," as in "sunken treasure" or "sunken eyes," is a separate, older participial form that survives only as a descriptive adjective rather than in the verb's ordinary perfect tenses, where "sunk" alone is used. The idiom 'sink or swim,' describing a situation with no middle ground between success and failure, pairs this verb with its close relative 'swim' in a single memorable phrase, both irregular verbs from the same broad Old English strong-verb tradition. One more figurative use worth noting is 'sink one's teeth into' something, meaning to engage deeply and enthusiastically with a task, a metaphor built on the physical image of biting down hard rather than literal submersion in water.

Across the tense system

"Sunk" and the adjective "sunken" split apart centuries ago into two different jobs: "sunk" for the true verbal participle ("the ship has sunk") and "sunken" for a permanent descriptive state ("a sunken ship," "sunken cheeks") — a divergence not every irregular verb develops, since most keep a single participle form for both jobs. The financial term 'sinking fund,' describing money set aside gradually to pay off a future debt, borrows the verb's -ing form directly into technical business vocabulary, a specialized use with no connection to water or literal sinking at all.

Common real mistakes

Using "sunk" as a plain simple past ("the stock sunk yesterday") instead of "sank" is increasingly common even in edited prose, reflecting a genuine ongoing shift in usage rather than a simple mistake. Confusing the adjective "sunken" with the verbal participle "sunk" (writing "has sunken" instead of "has sunk") is a separate, rarer error. A further point: 'sink' can be used causatively as well as intransitively — 'the torpedo sank the ship' (someone else caused the sinking) versus 'the ship sank' (it happened without an external agent named) — both perfectly grammatical and both sharing the identical irregular conjugation regardless of which pattern is used. One more minor point: the idiom 'sink in,' meaning for information to be gradually understood or absorbed mentally, is often used in the present tense without a helping verb ('it took a while to sink in'), keeping the base form rather than either irregular past form.

Examples

• The ship sank within twenty minutes of hitting the iceberg.
• Morale has sunk to an all-time low this quarter.
• The old dock sinks a little further each year.
• They were sinking deeper into debt every month.
• Had the boat sunk any faster, no one would have escaped.
• Her heart sank when she heard the news.
• Let's sink our teeth into this problem together.
• The sun is sinking below the horizon.

Memory trick

Pair "sink" with "drink" and "sing": sank/sunk mirrors drank/drunk and sang/sung, the same three-way i/a/u shift running through the whole family. Since "sunk" is creeping into casual use as a simple past too, the safest rule for formal writing is: no helping verb, use "sank"; helping verb present, use "sunk."