Learn Hardcore Turkish: Yemek masada soğudu. - The food cooled on the table.

The verb soğumak (to get cold) is made past-tense by removing -mak to get the stem soğu-, then adding the simple past suffix -du (which harmonizes to -du because of the preceding back vowel), with no extra ending for third person singular.
So:

Stem: soğu-
Past suffix: -du
Result: soğudu (“it got cold” or “it cooled” in the simple past).

What is the suffix -da in masada, and what does it indicate?

-da is the locative case suffix meaning “at/in/on.” Turkish attaches it to nouns to show location. Because masa has a back vowel a, the locative appears as -da. Thus masada literally means “at/on the table.”

Why is yemek not marked with any case ending?

In Turkish, the nominative (subject) case is unmarked, so subjects appear without a suffix. Additionally, only definite direct objects take the accusative suffix -ı/-i, and here yemek is the subject of an intransitive verb (there’s no direct object), so it stays simply yemek.

Who or what is doing the “cooling” in this sentence?

The subject yemek (the food) itself undergoes the action—because soğumak is intransitive, it means “to get cold” rather than “to cool something.” So “the food cooled” (the food got cold) on the table.

Why is there no pronoun like “it” in Yemek masada soğudu?

Turkish is a pro-drop language: subject pronouns are optional when the subject is clear from the noun or verb conjugation. Here, yemek names the subject, so you don’t need an extra “it” (o) in the sentence.

Is the word order fixed here, and could I say Masada yemek soğudu instead?

Turkish is relatively flexible, though the default shape for an intransitive sentence is Subject – Adverbial – Verb (S-Adv-V). Yemek masada soğudu follows that. You can front-focus the location by saying Masada yemek soğudu, shifting emphasis to where it happened but keeping the basic meaning “the food cooled on the table.”

What’s the difference between soğumak and soğutmak?

Soğumak is intransitive: “to get cold” (the subject cools itself).
Soğutmak is transitive: “to cool something” (an external agent causes the object to become cold).
If you said Yemeği masada soğuttular, it would mean “They cooled the food on the table.”

How do I know if -da means “on,” “in,” or “at” in a word like masada?

The locative -da simply marks spatial location. The exact English preposition depends on the noun’s inherent semantics. With flat surfaces like masa you naturally translate masada as “on the table.” With enclosed spaces like ev, evde is “in the house.” With places like okul, okulda is “at school.”