For questions about linguistic roots (e.g., reconstructed roots for proto-languages or roots for paragigms in inflected languages like Latin)

The distinction between the terms and can be fuzzy and is in general language dependent. For example in the Latin language:

  • am- is the root for 'love', with infinitive stem amã-, perfect stem amãv-, and participial stem amãt-
  • vid- is the root for 'see', with infinitive stem vidē-, perfect stem vīd-, and participial stem vīs-
  • aug- is the root for 'help', with infinitive stem augē-, perfect stem aux-, and participial stem auct-
  • cap- is the root for 'start', with infinitive stem capi-, perfect stem cēp-, and participial stem capt-

(Example taken form the answer by John Lawler in exile to What is the difference between a word root and a word stem?)