This is the 1632nd most frequent Turkish word.
tatili
"Tatili" means "the holiday" or "the vacation" in English.
'Tatili' is used as a direct object, referring to 'the vacation.'
Tatili erken planlamak önemlidir.
Planning the vacation early is important.
'Tatili' here serves the possessive context, indicating the 'vacation' of 'last summer.'
Geçen yaz tatili çok keyifliydi.
Last summer's vacation was very pleasant.
Similar to the first example, 'tatili' is the object being acted upon, describing 'the vacation.'