Greek breathing marks
Breathing marks
If a word in Greek starts with a vowel, diphthong or a letter ρ it must have a breathing markwritten above it. It is placed above the vowels and “rho” [ρ], and above the second letter in the diphthongs.
Greek has two breathing marks. It can be either roughor smooth.
The rough breathing mark( ῾ ) indicates that the first sound will have an initial “h” sound.
The smooth breathing mark( ᾿ ) indicates that this initial “h” sound is absent.
For example: ἕν [hén] one
ἐν [en] in
ἡμέρα [heméra] day
ἕξ [héks] six
ἀνήρ [anér] man, husband
Initial ρ and υ always have the rough breathing mark. If a word has two ρρ letters in it, the first one has a smoothand the second a roughbreathing mark, respectively. The breathing mark above ρ is silent.
For example:ὕδωρ [húdor] water
ῥῆμα [réma] word
ἐῤῥωμένος [erroménos] strong, vigorous
Source: https://greekforall.com