Learn Turkish: Çevreci olmak istersen, araba yerine bisiklet kullan. - If you want to be eco-friendly, use a bicycle instead of a car.

The word yerine means 'instead of' or literally 'to its place'. When you are talking about a general category of things, like 'a car' in general, you just use the plain noun before yerine. If you were talking about a specific car ('instead of the car'), you would need the genitive case: arabanın yerine.

How is the word çevreci (eco-friendly) formed?

It comes from the noun çevre, which means 'environment' or 'surroundings'. The suffix -ci is used to describe a person associated with a thing (like an occupation or an advocate). So çevreci translates to 'environmentalist' or 'eco-friendly'.

Let's break down the verb istersen (if you want). What suffixes are used here?

It is made of the verb root iste- (want), the aorist tense suffix -r (used for general, timeless statements), the conditional suffix -se (if), and the 'you' ending -n. Combining them makes istersen, meaning 'if you want'.

Why is kullan used without any tense endings?

Because it is an imperative (a command). When you give a direct command to a single person informally, you just use the plain root of the verb. Here, kullan means 'use!'.