I have learned a lot of new vocabulary/vocab today.

I have learned a lot of new vocabulary/vocab today.

Can that be used instead of "I have learned a lot of words today"? Feels a bit weird to use

The sentence with "vocabulary" is fine. Use "new words" instead of just "words" in your alternative.

What do you think is "weird" exactly? The word 'vocabulary'?

I might say I added to my vocabulary. (Not really.) More likely is I would say I learned a new word.

It's tricky at my age, because every time I learn something new I forget something I already knew.

jutfrank said:

What do you think is "weird" exactly? The word 'vocabulary'?

Click to expand...

Yes; I was a bit unclear with that. It feels weird to use singular even though I mean plural. Maybe, it also feels weird because I'm thinking of the phrase"to have a huge vocabulary" that's about the total sum of all words one knows and it feels weird to think of that when I'm saying I just learned a bunch of words.

There are quite a few words like that. That is, although grammatically they are singular they refer to more than one thing. For example, "furniture" always refers to more than one thing. The word "vocabulary" always refers to more than one word, but grammatically it's singular.

Can I use "vocabularies" in the sentence I used in my first post?
At first, I thought I couldn't because I've read in the dict.cc dictionary that "vocabularies" are word directories (which if I understand correctly are something like the alphabetical list of words such as the ones at the very end of English school books and not what I was referring to). But then I learned my cousins' English teacher seems to have used that word synonymously with "vocabulary" in a sentence such as "please learn the vocabularies of unit four". While no dictionary I checked explicitly suggested the latter usage, I've seen an entry that listed it as the plural of "vocabulary", "a list or collection of words"* (Merriam-Webster). I saw that the unit is subdivided into several stations, each containing their own vocabulary list. So, I thought perhaps the teacher may have done it right if they thought of unit four as several vocabulary lists.
What do you guys think?

*Please like my post if the quotation marks were done correctly.

"Vocabulary" isn't normally made into a plural.

An exception is, as you mentioned, when there is more than one "vocabulary" list or exercise in a book. Then it makes sense to refer to the different "vocabularies" in unit 4 of the book.

But, no, not in normal use.