Learn Turkish: Herkes bu talimatı hemen uygulasın. - Let everybody implement this instruction immediately.

The verb root is uygula- (to implement or apply). The suffix -sın makes it a third-person command. While English uses phrases like "let him do it" or "everybody must do it", Turkish just attaches -sın (or its vowel harmony variants) to the verb root. Here, it commands the subject (herkes) to do the action.

Since herkes means "everybody", why isn't the verb plural (uygulasınlar)?

In Turkish, indefinite pronouns that refer to a group or quantity, like herkes (everybody) or hiç kimse (nobody), are treated as grammatically singular. Therefore, the verb takes the singular imperative suffix -sın instead of the plural -sınlar.

Why is there an -ı on the end of talimatı?

The verb uygulamak takes a direct object. Because the instruction is specific, pointed out by the word bu (this), it requires the definite accusative case. Adding the -ı suffix to talimat marks it as the specific thing being implemented.

Normally, a word ending in "t" changes to "d" when a vowel is added. Why didn't talimat become talimadı?