Exception and substitution (be joz, be jâ-ye)

Substitution (به جای)

Use به جای to mean "instead of" or "in place of". Place it immediately before the noun or pronoun you are replacing.

You will often hear this structure when contrasting different materials or styles.

Exception (به جز)

Use به جز to mean "except" or "aside from". It sits right in front of the noun or pronoun it modifies.

You can also use it to point out a single detail you would change in an otherwise perfect piece.