You could say ''Kedvellek'' which means ''I like you'', although it is not as emphatic as ''Szeretlek''. You can say ''Szeretlek / I love you'' in many situations, just like in English ''I love you my son, I love my cat, I love this car of mine'' etc., and everyone will know it is not ''that'' kind of love as in ''I love my girlfriend''. Then there's ''Szerelmes vagyok'', I guess you might be looking for this one, it means ''I'm in love''.
Szerelmes vagyok a lányba - I am in love with the girl ( straightforward ) Szeretem a lányt - I love the girl ( may depend on the context ) Kedvelem a lányt - I like the girl ( maybe as a colleague or something )
Szerelmes vagyok a lányba, szerelmes vagyok a fiúba, szerelmes vagyok (te)beléd, szerelmes vagyok a nőbe and so on. You need an object and the ending (-ba, -be), literally ''into''. I'm sorry for my English, I hope this helps a bit.
"Szeretlek" is a verb form which includes a first-person singular subject and a second-person object. As you can see below, the distinct form to express a second-person object exists when the verb includes a first-person singular subject.
- I love = "szeretek"
- I love you = "szeretlek"
- I love him/her/it = "szeretem"
- You love = "szeretsz"
- You love him/her/it = "szereted"
- He/she/it loves = "szeret"
- He/she/it loves him/her/it = "szereti"
- We love = "szeretünk"
- We love him/her/it = "szeretjük"
- You love = "szerettek"
- You love him/her/it = "szeretitek"
- They love = "szeretnek"
- They love him/her/it = "szeretik"
It's a verb ending that's used specifically when
- the subject is first person singular ("I")
- and the object is second person ("you")
So szeretlek is specifically "I love you".
(A bit unusually, -lek/-lak is used regardless of whether the object is second person singular or second person plural.)
"he/they love(s) you" (and all others except "I love you") get the same word endings as without the "you" ...so the indefinite word ending, yes. But, you have to include the personal pronoun for the object to make it unambiguous:
- "Szeret engem." = he/she/it loves me
- "Szeret téged." = he/she/it loves you (sg.)
- "Szeretnek minket." = they love us
- "Szeretnek titeket." = they love you (pl.)
You would omit the object (engem/téged/...) if it's already unambiguous from the context who is being loved or not.
- "Szerinted szeret engem/téged? = Do you think he/she/it loves me/you (sg.)?
- "Szeret." = Yes, he/she/it does.
You could always include the object in the sentence. However, the natural way of speaking is that you always omit it when possible, and -lek is a word ending that carries even more information. Thus, you are even more likely to be able to omit the object when using -lek.
Note that in the last example, person B repeats the only part of speech from person A's sentence which he/she has emphasized. If emphasis had been on who is being loved instead of whether person A is being loved or not loved, the conversation would have gone like this:
- "Szerinted engem szeret?" = Do you think he/she/it loves me?
- "Téged." = Yes, you.