My wife made me think this morning about the verb “sink”.

Problem:
Some pairs of these verb forms are synonyms, which causes confusion.

Explanation:
My wife used the word “sunken” this morning.

This made me wonder about the difference between “sunk” and “sunken”.

And this led me to a dictionary.

The verb “sink” has these basic forms:

• Sink — present simple, as in “I sink when I do not dog-paddle.”
• Sank — preterite, as in “He sank my battleship!”
• Sunk — past participle, as in “She has sunk the deal.”
• Sinking — present continuous, as in “Hey, your boat is sinking!”

But here are the catches that lead to confusion:

• “Sunk” is often used as a synonym for “sank”.
• “Sunken” is definitely a synonym for “sunk”.

Putting the above two lists together, we see that the verb “sink” actually has these basic forms:

• Sink — present simple
• Sank or often Sunk — preterite
• Sunk or Sunken — past participle
• Sinking — present continuous

Solution:
I recommend avoiding “sunk” as a preterite and instead always using “sank” as the preterite. And I recommend using “sunk” in your writing and speech as the past participle but recognizing that “sunken” is a standard alternative as a past participle, especially in literary references such as “The pirates were looking for sunken treasure.”