How to write the word 'smart phone' in a research article? [closed]

  1. Smart phone
  2. Smartphone
  3. Smart-phone

I am really looking for some help regarding hyphen (-) issue in text found in research article. Is there any standard method how to use it?


This is a good question for referring to the Google Ngram Viewer, to see which is most popular lately.

If you look here:

enter image description here

You see that since 2000, smartphone has increasingly surpassed smart phone, with smart-phone virtually nonexistent.