Learn Hardcore Turkish: Ben çayı kaşıkla karıştırıyorum.

Ben means “I,” but Turkish is a pro-drop language—subject pronouns can be omitted because the verb ending already shows the subject. You could simply say Çayı kaşıkla karıştırıyorum and it still means “I am stirring the tea with a spoon.” You include ben mainly for emphasis or to contrast subjects.

What is the function of çayı and why does it end with -ı?

Çayı is “the tea” in the accusative case. Turkish marks definite (specific) direct objects with an accusative suffix (-ı/-i/-u/-ü). Here çay + -ı = çayı, indicating a particular tea. If you meant “I stir tea” in general (indefinite), you’d drop the suffix: Çay karıştırıyorum.

What does kaşıkla mean and why is -la used?

Kaşıkla means “with a spoon.” The suffix -la/-le is the instrumental case marker (equivalent to English “with”). Vowel harmony dictates -la after back vowels (a, ı, o, u), so kaşık + la = kaşıkla.

Why is the verb karıştırıyorum instead of karıştırmak?

Karıştırmak is the infinitive (“to stir”). To say “I am stirring,” you need the present continuous tense: start with the stem karıştır-, add the tense marker -ıyor, then the 1st person singular ending -um, yielding karıştırıyorum.

How do I know which vowel to use in -ıyor?

Turkish vowel harmony requires the vowel in -ıyor to match the last vowel in the stem. Since karıştır- has the back vowels a and ı, you use -ıyor (not -iyor, -üyor, or -iyor).

Why is the word order Subject-Object-(Instrument)-Verb?

Turkish generally follows SOV. Adverbial or instrumental phrases (like kaşıkla) precede the verb but can be moved around for emphasis. The verb almost always comes last:
• Ben çayı kaşıkla karıştırıyorum.
• Ben kaşıkla çayı karıştırıyorum.
Both are correct; the position shift just changes focus.

How would I change this sentence to past tense?

Replace the continuous suffix -ıyor with the past tense suffix -dı (vowel-harmonized) and keep -m for “I.” The stem karıştır- + -dı + -m = karıştırdım. So:
Ben çayı kaşıkla karıştırdım. (“I stirred the tea with a spoon.”)

Why is the verb stem karıştır- and not karış-?

Karışmak (intransitive) means “to get mixed” or “to interfere.” To express “to mix/stir something” (a transitive action), Turkish uses the causative form karıştırmak, adding -tır/-tir to make the verb take an object. Hence the stem karıştır-.