mayonnaise vs salad dressing

mayonnaise and salad dressing both are nouns.

Word	Noun	Adjective	Verb	Adverb
mayonnaise	Yes	No	No	No
salad dressing	Yes	No	No	No

As nouns, salad dressing is a hypernym of mayonnaise; that is, salad dressing is a word with a broader meaning than mayonnaise:

mayonnaise: egg yolks and oil and vinegar
salad dressing: savory dressings for salads; basically of two kinds: either the thin French or vinaigrette type or the creamy mayonnaise type

Other hypernyms of mayonnaise include dressing.

mayonnaise (noun)	salad dressing (noun)
egg yolks and oil and vinegar	savory dressings for salads; basically of two kinds: either the thin French or vinaigrette type or the creamy mayonnaise type