Learn Hardcore Turkish: Kupa sallanınca çay masaya sıçradı. - When the mug shook, tea splashed onto the table.

sallanınca comes from the intransitive verb root sallan- (“to shake”) plus the temporal-conjunction suffix -ınca, which means “when/once.” So: sallan- + -ınca → sallanınca (“when it shakes”).

What exactly does the suffix -ınca express here?

The suffix -ınca turns a verb into a “when/after” clause. It indicates that once the action of the verb is completed, the main clause follows. In English you’d say, “When the cup shook, the tea…”

Why is sallanmak used instead of sallamak?

sallanmak is the intransitive form (“to shake itself” or “to wobble”), so the cup is doing the action on its own. sallamak is transitive (“to shake something”). Since the cup isn’t shaking anything else but moving itself, we use sallanmak.

Why is the subject (“the cup”) not explicitly stated with a pronoun?

In Turkish, subjects (especially pronouns) are often dropped if they can be inferred. Here, sallanınca already implies “when it shakes,” so you don’t need o (“it/that”) before sallanınca.

What is the function of masaya? Why -ya and not -da?

masaya is the dative case of masa (“table”), marked by -ya because the tea jumps onto the table.
If you used masada (“on the table,” locative), it would mean “the tea hopped while already on the table,” which changes the sense.

What does sıçradı mean, and is it related to sıçratmak?

sıçradı is the past tense of sıçramak, meaning “to leap/splash.” It’s intransitive (“something leaps/splashes”).
sıçratmak is the causative (“to make something splash”), so you’d only use that if someone or something caused the splash.

Why is the word order çay masaya sıçradı instead of Subject-Verb-Object like English?

Turkish is an SOV (Subject-Object-Verb) language. Here:
Subject = çay, Object (goal) = masaya, Verb = sıçradı.
English orders S-V-O (“the tea splashed the table”), but Turkish places the verb last.

Could you say Kupa sallanınca masaya çay sıçradı instead?

You could, but it sounds less natural, because Turkish usually keeps the object (here masaya) close to the verb. Swapping çay and masaya is grammatically fine, but the typical flow is çay – masaya – sıçradı.