Sea is a noun: the salt water, or a named body of it. "The sea was rough on Tuesday." See is a verb: to perceive with your eyes, or to understand. "I can see the lighthouse from here." They sound identical, so only spelling separates them.
A thing versus an action
Sea is something you can point at. It takes the, and it can be plural.
- They walked along the sea front.
- The Baltic Sea freezes in places.
- Rough seas delayed the ferry.
See is something you do. It has a subject and, usually, an object.
- Did you see the email I forwarded?
- I'll see you on Thursday.
- Ah, I see what you mean.
The memory trick
You see with two eyes — and see has two e's. If eyes or understanding are involved, use the double e.
For the other, note the a in sea, and the a in salt, sand and sail. Water words take the a.
The test
Try putting the in front. "The sea" works; "the see" does not. Then try swapping in look at or understand. If either fits, you want see: "I see the problem" → "I understand the problem".
See is more than eyesight
Quite a lot of see's work has nothing to do with vision at all, which can throw people:
- Understanding: I see why you're annoyed.
- Meeting: She's seeing a specialist next week.
- Checking: See whether the shop's still open.
- Experiencing: The building has seen better days.
All of these take the double e. The rule of thumb still holds: if it's a doing word, it's see.
Watch the endings
- See → saw (past), seen (with have): I saw her yesterday. I've seen that film. Not "I seen her yesterday" in standard writing.
- Sea → seas, plural only. It has no past tense, because it isn't a verb — a useful check in itself.
- Sees (he sees) and seas (rough seas) are yet another homophone pair caught in the same trap.
Compounds to keep apart
Sea: seaside, seafood, seasick, seashell, seaweed, seabed, overseas. See: foresee, oversee, sightseeing, see-through. Note that overseas (abroad, across the water) and oversees (supervises) are different words: She oversees the overseas offices.
Frequently Asked Questions
Is it "I can see the sea" or "I can sea the see"?
I can see the sea. The verb comes first with two e's, and the water takes the a. It's a useful sentence to keep as a check.
What's the difference between "seas" and "sees"?
"Seas" is the plural of sea — "calm seas ahead". "Sees" is the verb with an s — "he sees the point".
Is it "overseas" or "oversees"?
Overseas means abroad: "an overseas posting". Oversees means supervises: "she oversees the department". Different words, different meanings.