Yes, fax is a word.
“Fax” can be used to describe:
- A document that has been sent as a fax transmission.
- A fax machine (a machine that can send and receive fax transmissions).
- The act of sending a fax (using a fax machine to send and receive a fax transmission).
“Fax” can be used as a verb (“Please fax this paperwork to Sally”) or a noun (“Somebody forgot to fill the fax with toner”).
The past tense of fax is “faxed” (Sally faxed me the document last night).
The future tense of fax is “fax” (I will fax Sally the document later today).