Form versus orthography versus spelling

Question

What is the proper linguistic term for the way a word is written?

Initially, I used the term form, but then I was told that it was orthography. However, I sometimes come up with sources where the term form is used. And some suggest an alternative term is spelling. (Also, there is morphology; I guess that term encompasses more than I am looking for.) Are these interchangeable terms? Taking the above quote as an example:

Inflection, formerly flection or accidence, in linguistics, the change in the form of a word (in English, usually the addition of endings) to mark such distinctions as tense, person, number, gender, mood, voice, and case.

(1) Which of the three—form - orthography - spelling—would be the correct usage? (2) If they are not interchangeable, what subtleties each would carry?

Answer 1

I would be inclined to pair spelling with orthography as orthography is "the conventional spelling system of a language". Form is then more generally used to refer to how the word looks, and for example morphology influences the forms of words but the forms possible (e.g. in inflection, derivation, etc.) do not deviate from the accepted spelling/orthography as they are part of the system. An example would be the change of spelling in "teddy"/"teddies". This is generally a change in form (y>i) that happens according to the orthographic rules of English.