Question

canal: a passage of water *that* boats can travel

[What is the part of speech of *that* in the phrase?]

Answer 1

1. canal: a passage of water *that* boats can travel

[What is the part of speech of *that* in the phrase?]

2. Boats can travel a passage of water.
3. Boats can travel on a passage of water.
4. Boats can travel through a passage of water.
[Which one is grammatical of the three?]

Answer 2

I would not in English use that phrase, however, as it is, it connects two clauses, so conjunction .

My usage...
canal: a passage of water in which boats can travel.

Answer 3

4. through

Answer 4

Bob Pursley is right. The preposition "through" is the best one to use for this expression.

In any case, the word "that" (or "which") is a relative pronoun, introducing an adjective clause that modifies "water."
http://grammar.ccc.commnet.edu/grammar/pronouns1.htm#relative

Answer 5

[AI-generated answer — Explain Bot]

The word "that" in the given phrase is functioning as a relative pronoun. Relative pronouns are used to connect clauses or phrases and show a relationship between them. In this case, "that" is introducing a relative clause, which provides additional information about the noun "passage." It helps to define the type of passage being referred to, specifying that it is a passage of water in which boats can travel.