Verbal nouns (fiilden isim yapma ekleri / mastarlar) are nouns formed from verbs. They represent the action or state of the verb itself. Turkish has several common suffixes for this.

1. The Infinitive Suffix: -mek / -mak

This is the dictionary form of the verb and functions as a verbal noun meaning "the act of doing X" or "to do X." It can take noun case endings.

• Okumak güzeldir. (Reading (the act of reading) is beautiful.)
• Yüzmeyi seviyorum. (I love swimming (the act of swimming).) (yüzmek + -i accusative)
• Gitmek istemiyorum. (I don't want to go.)

2. The -me / -ma Suffix

This suffix (A-Type vowel harmony) forms a verbal noun that is very common and versatile, often corresponding to the English "-ing" form used as a noun or a gerund phrase.

• gülmek (to laugh) → gülme (laughing, the act of laughing)
• konuşmak (to speak) → konuşma (speaking, speech)
• Onun gelmesini bekliyorum. (I am waiting for his/her coming.) (gelme + -si (possessive) + -ni (accusative))
• Sigara içmek yasaktır. / Sigara içilmesi yasaktır. (Smoking is forbidden.) (Here, içme can be used like içmek)

3. The -iş / -ış / -uş / -üş Suffix

This suffix (I-Type vowel harmony) forms a verbal noun that often emphasizes the manner, style, or a single instance of the action.

• bakmak (to look) → bakış (a look, gaze, manner of looking)
• yürümek (to walk) → yürüyüş (a walk, manner of walking, a march)
• giriş (entrance, entry) (from girmek - to enter)
• çıkış (exit) (from çıkmak - to exit)

All these verbal nouns can take case endings and possessive suffixes just like regular nouns.