difference between 伤痕， 伤疤 and 疤痕？ Recently, I read that someone's  额头上有一个伤痕 。   I knew that the sentence literally meant that there was a scar. But then I thought "Why didn't they say "伤疤” or “疤痕”。 All three of these translate to scar in english, is there any simple way to divide them in Chinese?
Often "疤痕" is reserved for "physical scar", while "傷疤" and "傷痕" can mean more; they can even mean a mental scar.

Therefore, being a 疤痕 implies being a 傷疤 (resp. 傷痕); being a 傷疤 (resp. 傷痕) not necessarily implies being a 疤痕.

Nevertheless, please bear in mind that these distinctions are subtle and not dogmatic. :)