That's what percent is - a multipleir - 88% is 88% of something, 300% is 300% of sometjhing or 3 times something . So it seems to me the easist way to think of the lack of units used/needed for line-height is to think percent and don't use the percent symbol nor any symbot nor anything for units. What do you think?
Yes, basically. Think of line-height as a super-imposed fontsize in 'ghost' container
WHEN DEALING WITH FONTS EMs and %s act similarly that is 1em and 100% = 1 x the size of the fontsize of the parent element. line-height also gives you the option to use a unit less value (where 1= 100%) AND to use ABSOLUTE units: PX, PT, IN, etc. On occasion , these can be handy too.