From what I understand, "食べましょう" and "食べよう" both imply, more or less, the same meaning, which is 'to invite someone to eat with them', the latter being a verb conjugation of the volitional form, the more casual 'ましょう'.
However, "食べる", the base verb which means 'to eat', is much more commonly used for the invitation message. I would like to know why that is so, and when have people started to use it, so much so, that is has become a colloquial phenomenon.
Thank you.
However, "食べる", the base verb which means 'to eat', is much more commonly used for the invitation message.
No. 食べる is not used as an invitation like ～ましょう/～よう, both of which roughly mean "Let's eat it". The plain form is used in the following situations:
To state the speaker's own will
食べる!
I'll eat it!
As a question to check someone's will (used with a rising intonation)
食べる? ⤴
Wanna eat?
(Note that this can sometimes work as a casual invitation, but basically it's just a question.)
Less commonly, as an imperative (used by a parent, teacher, etc. Plain form as imperative)
食べる!
Eat it!
