vicegerent / successor / steward
Feminine in form (tāʾ marbūṭa) but refers to a male (Adam). Plural: خُلَفَاءُ (khulafāʾ). From خَلَفَ (to succeed/follow after).
Humanity's role as God's khalīfah on earth implies stewardship and moral responsibility - a cornerstone of Islamic environmental and social ethics.