In Dao De Jing, 常 should be translated as "eternal" or as "common"? I'm doing a translation of the Dao De Jing, using some originals and some translations to english and portuguese. I've noticed that 常 chang is almost always translated as "eternal", "fixed", "immutable", etc. That seems to be a monotheistic preconception, far from the natural view of the world that seems prevailing in the book. So I'm using "common" or "usual" - another translation of the term, and one that seems to fit better in the overall meaning of the text. After all, not everything "common" is "unchangeable". Has anyone else thought about it? Which translation do you think is more adequate to the spirit of the original? Another question is: each chinese character should receive only one translation throughout the book? (Maybe that's a silly idea, maybe not.) Thanks in advance!
This article suggests that the original text was 道可道，非恒道. That is, 恒 not 常 (meaning 永恒 = eternal, unchanging).

This  dictionary definition for 常 also includes the meaning "长久，经久不变" (and gives the example 常量, with an alternate form 恒量).