h- is prefixed to an initial vowel of a stressed word when a preceding connected but unstressed word ends in a vowel, and, had the word begun with a consonant, no mutation would have been appropriate.
 

(2) In nouns and verbal nouns after 'e' fem.

(3) In nouns after the genitive feminine singular of the article ny

(4) after ny the plural of the article; these cases are not always written

(5) After dy before an adjective, forming an adverb; not always written