As per my knowledge, and as per Britannica, a chord actually uses three or more notes. A two note structure is called a diad, which implies a bit of confusion in the term "power chord" (written as 5, as in G5, which == G D == 1 5).. as it is not by definition a chord but a diad.
This may be a pedantic clarification, but that is the definition
TBH "definition" depends on the theory from which you're looking at the notes.
In the eyes of the Common Practice two simultaneous notes are not chords; in rock they most definitely are; in EDM you don't even care, since timbre is all that matters; in jazz you'd say "it depends" (e.g. might even be a triad with an omitted 5th... depending on context!)
This may be a pedantic clarification, but that is the definition