what's the difference between "I havn't felt tired" and " I haven't felt tired yet"?
"I haven't felt tired" I think this sentence has two meaning. First meaning:I am not tired now. Second meaning: I never felt tired in the past. I am an energetic person.

" I haven't felt tired yet" ,I think it only hasthe first meaning (I am not tired now). so yet here is very important to express the meaning pricisely.

Am I right? please help me. Thank you very much.

Question

what's the difference between "I havn't felt tired" and " I haven't felt tired yet"?
"I haven't felt tired"   I think this sentence has two meaning. First meaning:I am not tired now. Second meaning: I never felt tired in the past. I am an energetic person.

" I haven't felt tired yet" ,I think it only hasthe first meaning (I am not tired now).  so yet here is very important to express the meaning pricisely.

Am I right? please help me. Thank you very much.

Answer

"I haven't felt tired" means that LATELY you haven't felt tired (e.g., "I've only been sleeping 5 hours a night this week, but I haven't felt tired").

"I haven't felt tired yet" means the same thing.  However, if you change it to, "I don't feel tired yet" this would mean that the activity you are doing AT THE MOMENT is not making you tired (e.g., "I've been on this treadmill for 20 minutes, but I don't feel tired yet").

Answer

The first sentence is tricky because it's a kind of oxymoron -- it's a "finished" action which had been never reached. I would translate it as "I have not reached [the stage of feeling/being tired] [at the moment]". If it was in the past, it would be "I hadn't felt tired (yesterday)". But usually, people would say "I wasn't tired yesterday".
In the second sentence, "yet" adds the time element, now/until now.