Muda wa kuvuka maili moja ya bahari ni mrefu.

Wa is the linking word that means something like of or for, and here it connects muda with the action kuvuka.

So:

• muda = time
• wa = of / for
• kuvuka = to cross / crossing

Together, muda wa kuvuka means the time for crossing or the time to cross.

It is specifically wa because muda belongs to a noun class that uses wa for this kind of connection.

Kuvuka is the infinitive form of the verb, like to cross in English.

In Swahili, the ku- form can act like:

• a verb meaning to ...
• or a verbal noun, like crossing

So in muda wa kuvuka, the phrase literally works like time of crossing or time to cross.

This is very normal in Swahili. For example:

• nafasi ya kusoma = time/chance to study
• njia ya kwenda = way to go
• muda wa kusubiri = time to wait

Maili is a borrowed noun, and in normal usage it usually stays maili for both singular and plural.

So:

• maili moja = one mile
• maili mbili = two miles

This is common with some loanwords in Swahili. The number tells you whether it is singular or plural.

Ya bahari literally means of the sea.

So:

• maili ya bahari = sea mile / nautical mile

In smoother English, that is nautical mile.

The ya links maili and bahari. It means that the mile is being specified as a sea/nautical mile, not just any mile.

Because moja modifies maili, not bahari.

So the structure is:

• maili moja = one mile
• ya bahari = of the sea / nautical

Putting them together:

• maili moja ya bahari = one nautical mile

If you said maili ya bahari moja, it would sound like a sea mile of one sea, which is not the intended meaning.

The adjective root is -refu, meaning long or tall, but Swahili adjectives usually take an agreement prefix that matches the noun they describe.

Here the noun being described is muda, so the adjective appears as mrefu.

That m- shows agreement with muda.

So:

• -refu = long/tall
• mrefu = long, agreeing with muda

This is an important Swahili pattern: adjectives often change shape to match the noun class of the noun.

Ni is the copula here, meaning something like is.

So:

• Muda wa kuvuka maili moja ya bahari ni mrefu
• literally: The time for crossing one nautical mile is long

In Swahili, when you make a sentence like X is Y, ni is very often used.

So ni mrefu means is long.

The main noun of the subject is muda.

That is why you get:

• wa in muda wa kuvuka
• mrefu in ni mrefu

Even though the subject contains a longer phrase, the head noun is still muda. The whole subject is muda wa kuvuka maili moja ya bahari, but grammatically the key noun is muda.

So the sentence is really built around:

• muda ... ni mrefu
• the time ... is long

Because Swahili does not normally use articles like English the and a/an.

Whether a noun is understood as the time, a time, or just time depends on context.

So muda can mean:

• time
• the time
• a time

depending on the situation.

This is completely normal in Swahili.

This sentence is grammatical and understandable, but Swahili often also expresses this kind of idea with -chukua muda or similar wording.

For example, another natural way might be:

• Inachukua muda mrefu kuvuka maili moja ya bahari. = It takes a long time to cross one nautical mile.

The given sentence is more literally structured as:

• The time for crossing one nautical mile is long.

So yes, it works, but depending on context, a speaker might choose a different phrasing that sounds more everyday or more direct.