:salamext:
I'll try and explain in English inshaAllah (actually I'm gonna cheat lol)
ممنوع من الصرف (the diptote- Ghair munsarif)
It is a mu'rab (declinable) noun which does not accept the tanween.
It is of 2 kinds:
a) Nouns which do not accept tanween for only one reason
b) Nouns which do not accept tyanween for two reasons
Nouns which do not accept tanween for only 1 reason
This reason is
 one of the two following things:
A) 
ألف التأنيث (The alif signifying femininity) 
It is either
 مقصورة (short) or 
ممدودة (elongated)
The first is a long 
aa written in Arabic with a 
yaa (ى )
and the second is a long 
aa followed by followed by a 
hamza (اء )
and both these should be extra, added after the third radical (ie after the third root letter of the word) eg:
ألف التأنيث المقصورة: 
فتاوى  هدايا  حبلى  دنيا  مرضى
ألف التأنيث الممدودة: 
فقراء  أصدقاء  حمراء  صحراء
B) 
الجمع المتناهي that is the plural on the patterns of 
مفاعل (mafaa'ilu) and 
 مفاعيل (mafaa'
iilu) eg: 
فنادق  أنامل  حدائق  مفاتيح  أسابيع
Even 
singular nouns on these two patterns are diptotes eg:
طماطم طباشير
(Taken from third Madinah book)
I'll post the rest later inshaAllah
