For Aristotle, "form" is still what phenomena are based on, but is "instantiated" in a particular substance.
fɔːɹ ˈæɹɪstˌɑːɾəl, "fˈɔːɹm" ɪz stˈɪl wʌt fɪnˈɑːmɪnə ɑːɹ bˈeɪst ˈɔn, bˌʌt ɪz "ɪnstˈænʃɪˌeɪɾᵻd" ɪn ɐ pɚtˈɪkjʊlɚ sˈʌbstəns.