Turkish nouns take case endings (suffixes) based (in part) on the part of speech they are used for in the sentence. If a noun is being used the subject of the sentence, it will not have any special suffix (Nominative case). If it is being used as an object, it will have a -i/-ı/-ü/-u ending (Accusative case). Other endings are used for other parts of speech. Additionally, some verbs require the preceding noun to take a certain case. Sevmek is an example of this type of verb. A noun associated with Sevmek will always be in the accusative form. Some verbs do not require the preceding noun to be in any specific case, so you can see their nouns taking any number of different case endings. The -i suffix is used for the accusative case in Turkish. It is used on words which are the object of the sentence and usually on a word which in English would be preceded by 'the'. Also, some verbs (such as sevmek) require the accusative case. Any time you see the verb 'sevmek,' there will be an associated noun taking the accusative form (-i). You should memorize the most common words which require the accusative form. This will save you a lot of trouble. =) Some words requiring accusative case endings include: açmak (kapıyı açıyorum) anlamak (seni anlıyorum) görmek (onları görüyorum) For a more complete list, take a look here: http://quizlet.com/3095386/turkish-common-verbs-requiring-accusative-endings-flash-cards/ The verb 'istemek' does not require accusative case, so you can see 'öğrenmek istiyorum.' Accusative is (for me) the most difficult aspect of Turkish. I still get it wrong sometimes. I hope my explanation makes it a bit clearer for you! Good luck =)

This question is about Verbals, that is, ‘fiilimsi‘. In Turkish, there are several participles, in other words ‘verbal -noun suffixes’, such as yı. As is the case with English, we mostly make a complex sentence with relative clauses however, we use postfixes which follow the verb. for example okumak means studying bu with suffixes yı It will be used as a noun ,Ben okumayi öğrendim I had learned the reading ,I think you have to google the title 'fiilimsi' which is one of the most important thing in Turkish grammar.

only thing you should know about it is when you say çalışmayı it is actually çalışmak-ı, but if it kind of soften k letter to y letter. For example görmek *görmeyi hatırlamak*hatırlamayı bilmek*bilmeyi vowels changes consonant k to y or ğ letter it sometimes becomes görmedik* görmediği hatırlamadık*hatırlamadığı bilmedik* bilmediği p.s. it is all my analysis and you cant find in anywhere easily :D

Because "istiyorum" and "seviyorum" need accusative case. Rose's answer is great.