Can a sentence-ending particle like よ be used to express multiple nuances at once?

Question

Example: 知らないよ in response to someone thinking you know, even though you don’t.

Using wikitionary for particle lookup, I found these 2 uses of よ that could fit the context:

• indicating statement of certainty (I don't know, you know. / I'm certain that I don't know.)
• indicating emphasis (I don’t know!)

There are also some other sources that say よ can be used to emphasize feeling (I really don't know), or to contradict (you thought I know, but I don't know).

Is it possible for multiple uses of a particle to be in use at the same time, or is there always one usage that's most correct?

Answer 1

It is impossible to unarguably classify the use of such words into a finite number of categories.

Have you ever wondered how many ways "hey" is used in English, and how it should be strictly categorized? If you look up an English dictionary, several usages of "hey" are listed. In some dictionaries, usages such as "hey expressing surprise" and "hey indicating lack of interest" might be listed, but such categorization differs from dictionary to dictionary. Of course this does not mean you can't use "hey" without knowing all of these.

The same is true for the particle よ. While some usages of よ can be clearly distinguished from others (e.g., vocative-よ is relatively distinct), the nuances of よ as a sentence-ending particle vary, and it is impossible to categorize them strictly. You cannot assume there is always only one correct definition when the number of definitions is indefinite in the first place.