ilgeçler — postpositions and the cases they take
Turkish doesn't have prepositions; it has postpositions — they come after the noun. Each postposition demands a particular case on the noun before it. ile ('with') and için ('for') take the bare/genitive depending on word type. kadar ('as much as / until') takes the bare or dative. gibi ('like') takes the bare. sonra ('after') and önce ('before') take the ablative -den/-dan. Once you know which case each postposition demands, you have the equivalent of dozens of English prepositions.
ile — 'with' / 'and' / 'by means of'
ile can mean 'with' (instrument or company), 'by' (means of transport), or even 'and' joining two nouns. Common nouns take ile in the bare form: kalem ile ('with a pen'), otobüs ile ('by bus'), arkadaşım ile ('with my friend'). Pronouns take the genitive: benim ile ('with me'), senin ile ('with you'), onun ile ('with him/her'). In speech and writing, ile very often clitisizes onto the noun as -(y)la / -(y)le by harmony: kalemle, otobüsle, benimle, seninle. The two are equivalent — pick whichever feels lighter.
için — 'for' / 'in order to' / 'because'
için has three roles. (1) Beneficiary 'for': senin için bir hediye = 'a gift for you' — pronouns take genitive, common nouns the bare form: kardeşim için = 'for my sibling'. (2) Purpose 'in order to', after an infinitive: görmek için geldim = 'I came in order to see'. (3) Reason 'because of', on a clause: geç kaldığı için özür diledi = 'he apologized because he was late' — note the participle kaldığı + için.
kadar — 'as much as' / 'until' / 'about'
kadar is the same word you used for comparisons. Three more uses. (1) 'Until', with a dative on the time word: akşama kadar = 'until evening', saat üçe kadar = 'until 3 o'clock'. (2) 'As much as / as many as' for quantity: iki kilo kadar = 'about two kilos / as much as two kilos'. (3) 'About / approximately': on kadar kişi = 'about ten people'. With pronouns: genitive — benim kadar, senin kadar.
gibi — 'like' / 'as'
gibi takes the bare form (or genitive on pronouns) and means 'like / similar to'. Bir aslan gibi güçlü = 'strong as a lion'. Onun gibi konuşma = 'don't talk like him'. With clauses, gibi also means 'as if / it seems': Yağmur yağacak gibi = 'It looks like it's going to rain' (lit. 'rain will fall like'). gibi gibi doubled gives 'sort of / kind of': iyi gibi gibi is colloquial for 'okay-ish'.
sonra and önce — 'after' / 'before' (ablative)
Both take the ablative -den/-dan on the time word. Yemekten sonra = 'after dinner'. Saat üçten önce = 'before 3'. Senden sonra geldim = 'I came after you'. With a verbal clause, use the converbs you've already met: yemek yedikten sonra ('after eating'), gitmeden önce ('before going'). Memorize: -den sonra = 'after', -den önce = 'before'. Note: order is time-word + ablative + sonra/önce, never the reverse.
