Causative suffixes are attached to intransitive verbs to make them transitive.

They also attach to transitive verbs to indicate further involvement of another object/agent. In this case, this other agent is an indirect object receiving a dative suffix, since the original verb already took a direct object.

I made my aunt buy leather from the market.

Teyzeme çarşıdan deri aldırdım.

Unfortunately there are six forms of this suffix, and the rules for using them are not entirely regular. The suffixes are:

-Dİr : öldürmek (to kill), aldırmak (to make someone buy)

-t : kısaltmak (to make something shorter), tanıtmak (to introduce someone or something)

-İt : sapıtmak (to go haywire), korkutmak (to scare someone)

-İr : bitirmek (to end something), düşürmek (to drop something)

-Ar : çıkarmak (to extract something)

-Art : çökertmek (to make something collapse)

The causative suffix is -t for all polysyllabic verbs that end in an r or an l, and there are about 30 monosyllabic verbs for which the suffix is either -İt, -İr, -Ar or -Art.

All other verbs take -Dİr as the causative suffix, which is the most common form.

Additionaly, there are some verbs that don't follow any of the six rules above, the most common of which you can see below.

Turkish Intransitive	English	Turkish Transitive	English
girmek	to enter	sokmak	to insert, to make it enter
gelmek	to come	getirmek	to bring, to make it come
gitmek	to go	götürmek	to take it (away from the speaker)
kalkmak	to rise up	kaldırmak	to lift, to raise