Solstitium aestate venit.

The verb is venit, so the sentence needs something that comes. That something is solstitium.

A quick grammatical breakdown:

• solstitium = a noun in the nominative singular here, so it is the subject
• aestate = a noun in the ablative singular, so it is not the subject
• venit = he/she/it comes or, in another context, came

So the basic structure is:

• solstitium = the thing doing the action
• venit = the action
• aestate = when it happens

That is a very common beginner question. -um does often mark the accusative singular in the second declension, but with neuter nouns it can also be the nominative singular.

Solstitium is a second-declension neuter noun. In neuter nouns:

• nominative singular often ends in -um
• accusative singular also ends in -um

So solstitium can be nominative or accusative depending on its role in the sentence. Here, because it is the thing that comes, it is nominative and therefore the subject.

Aestate is ablative singular of aestas, meaning summer.

Its ending -e is a common third-declension ablative singular ending. So:

• dictionary form: aestas
• form in the sentence: aestate

Here it is being used as an ablative of time when.

Because Latin often uses the ablative case by itself to express time when.

So:

• aestate = in summer
• hieme = in winter
• anno = in the year

English usually needs a preposition such as in, but Latin often does not. The case ending already carries that idea.

Yes, Latin can use in with time expressions, but in a simple sentence like this it is very natural to use the bare ablative:

• aestate = in summer

So the version without in is not missing anything. It is a normal Latin way to say it.

Here it is understood as present tense: comes.

However, in ordinary Latin spelling venit can be ambiguous, because it may represent either:

• venit = comes
• vēnit = came / has come

When macrons are not written, context tells you which meaning is intended. In this sentence, the intended meaning is the present: comes.

Latin has no articles. It does not have separate words for the or a/an.

So solstitium could mean:

• the solstice
• a solstice

Context decides which English article is best. In this sentence, English naturally uses the.

Not very. Latin word order is much more flexible than English word order because the endings show each word's role.

This sentence means the same basic thing in several orders, for example:

• Solstitium aestate venit
• Aestate solstitium venit
• Solstitium venit aestate

The exact order can change emphasis or style, but the grammar stays clear because of the case endings and the verb form.

You would look them up under these dictionary forms:

• solstitium, solstitii or solstitium, -i n. = solstice
• aestas, aestatis f. = summer
• venio, venire, veni, ventum = come

This matters because aestate is not the headword form. It is an inflected form of aestas.

They belong to different declensions:

• solstitium = second declension, neuter
• aestas = third declension, feminine

That helps explain their forms:

• solstitium has nominative singular -um
• aestate is the ablative singular of aestas

So this sentence is also a nice example of how Latin uses different noun patterns in the same sentence.