question on the phrase "wakaranain jya nai"

[yellowjello]

while reading a manga i came across the phrase "wakaranain jya nai" and i'm not sure what it means. i know that "wakaru" means to know, to understand while jya nai is the colloquial form of de wa nai and means "not."
so is this phrase a double negative and actually means that the person does understand? or is it something else?

 

[Mike Cash]

ん is a contraction of the explanatory の, about which there are recent threads.

 

[charusu]

分らない is the plain form negative conjugation of 分る.

Read up on the use of のだ／んだ (のです／んです）as Mike suggests (Noun-related Particles | Tae Kim's Guide to Learning Japanese).

I would translate it as "It's not that don't know/understand".



分らない should be 分からない, JRef won't let me correct my typo. Although it seems that 分らない may be correct too...

 

[yellowjello]

ah i did not realize that it was the のです form. thanks for the clarification and the helpful link as well.