In case of Ism

mabni

Mu’rab

Ism containing three letters.

Ism with more than three letters

In the case of mabni ism except for these five cases    أَلًى ، أَنَّى ، مَتَى ، لَدَى، أُوْلَى ا  is written. example-أَنَا، هٰذَا 

If derived from و  then it would be ا example-عصَا

and if derived from ي it will be ى example-هُدًى

1) In the case of name referring to the nation if there is ي before alif then it will be ا example-دُنْيَا   otherwise it will be ى. example-مُشْتَشْفَى . But in case of name if there is ي before alif it will be ى  example-يَحْيَى

2) In the case of non-Arabic name, it will always be  ا   .example-فَرَنْسَا ، أَمْرِيْكَا   but there is some exception like

مُوْسَى  عِيْسَى،  كَسْرَى etc.

For Fi’l

Three lettered fi’l

Fi’l with more than three letters

If the alif is derived from و  it will beا  , if it is derived form ي it will be ى  example-دَعَا   عَفَا،  مَشَى    

This can be remembered in the way like if there is و orء in the middle of the word, there will be ى  at the end,  example-جَوَى، وَقَى، شَأَى، بَأَى

In the case of a word with more than three letters, if there is ي before the last alif, it will beا . example-أَحْيَا   otherwise it will be ى. example-اِنْتَهَى

In case of harf

إلَى، عَلَى، حَتَّى، بَلَى : except these four, there will be ا   in all harf example-لَا، أَلَّا، كَلَّا، عَدَا

I don't know its meaning

لَا أَدْرِي مَعْنَاهُ

مَعْنَى + هُ  = مَعْنَاهُ

He ironed it

كَوَاهُ

كَوَى + هُ   = كَوَاهُ

Bukhari narrated it.

رَوَاهُ الْبُخَارِي

رَوَى + هُ  = رَوَاهُ