A Japanese person that was born in Nagoya wrote on instagram a very short
sentence: 年賀状に使えるな that I'm not able to translate. Different online
translators give opposite results. The [TanoshiJapanese
dictionary](https://www.tanoshiijapanese.com/dictionary/entry_details.cfm?entry_id=97489)
doesn't help me distinguish between meanings 1) and 3).

  * How would you interprete the "な" at the end of the sentence?
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2020-09-15T14:13:25.313
80664
2020-09-17T00:45:03.180
39873
question
particle-な
Interpreting な in 年賀状に使えるな
To break it down:

年賀状 "new years card"  
に "as, for, for the purpose of"  
使える "can use" "be usable" -- potential form of 使う  
な -- sentence ending particle (終助詞) for 詠嘆, 推量, 納得, etc.

> 年賀状に使えるな。

The な here can indicate light exclamation, conjecture, or maybe conviction. So
it can mean something like:

> "It can be used as a new years card(, I think/suppose)."  
>  "(I think / I'm sure) I can use it as a new years card."

A few examples of this な:

> かわいいな。 Oh that's cute.  
>  いい天気だな。 What a nice day.  
>  お[腹]{なか}が[空]{す}いたな。 I feel hungry.  
>  明日は晴れるな。 (I think) it'll be sunny tomorrow.

* * *

It cannot be negative imperative ("Don't ~~!") in your example since 使える is
the potential form.

Compare:  
使いな。 -- light command  
使うな。 -- negative imperative
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2020-09-16T06:12:00.667
80684
2020-09-17T00:45:03.180
2020-09-17T00:45:03.180
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answer