I thought that you were supposed to use the conjugated version of
comer when referring to the subject, but I see sentences formed like the first example. So what is the difference between both sentences? Which is the correct one?
First of all, the correct answer is:
No puedo comer
Which means "I can not eat". Then, "No puedo como" will be:
I can't as
So, the main difference between these sentences is that "
comer" is a verb (to eat) and
como is a comparison element. However,
como belongs to the verb to eat as well. Example:
No como carne = I don't eat meat
No como la misma carne como mi padre = I don't eat the same meat than my father
In conclusion, the first person of the verb "
como (Yo como) but
como is also a comparison element. Hope i helped you.
No puedo comer is the direct translation of "I cannot eat".
When you conjugate the verb "poder" as "puedo" you are already conjugating the main syntactical verb in the predicate. In this case, "comer" is not the main verb in the sentence and must not be conjugated to match the subject "yo". This particular construction is a "perífrasis verbal", verbal periphrasis, where the first verb ("poder") is an auxiliary verb which modifies the meaning of the second verb ("comer"), which has the real meaning.
So, the verb with the meaning (comer) is not conjugated, whereas the auxiliary verb (poder) is the one conjugated in the sentence. This happens with all verbal periphrasis: "Yo te pido salir" (I ask you to exit), " Te sugieren aparecer" (They suggest you appear), etc, etc.
I think you might be able to grasp why this is this way if you think of the verbe "poder" as "to be able to"
Yo no puedo comer = I am not able to eat
In that case, in english you also use an infinitive.
Hope I could help!