α. early Old English feowerteogþa, Old English feowertegoða, Old English feowertegða, Old English feowerteogaða (rare), Old English feowerteogeþa, Old English feowerteogeða, Old English feowerteogoða, Old English feowerteogða, Old English feowerteoþa, Old English feowerteoða, Old English feowertigeþa, Old English feowertigeða, Old English feowertigoþa, Old English feowertigoða, Old English feowertigþa (rare), Old English feowertigða, Old English feowertugeða (rare), Old English feowertygeþa (rare), Old English feowertygeða (rare), late Old English feorwertigeþa, late Old English feowertihð- (inflected form), late Old English fęwertegeð- (inflected form), late Old English fowertigeð- (inflected form), early Middle English feortiȝeþe, early Middle English feortuȝeþ- (inflected form), early Middle English feortyȝeþe, early Middle English feowerteoðe, early Middle English feowertiȝeþe, early Middle English fourteoþe, early Middle English fowertiȝthe, early Middle English fowertiðe, early Middle English fowertuðe, early Middle English furteohte, early Middle English fuwertiðe, Middle English fourtied, Middle English fourtithe, Middle English fourtiþe, Middle English uourtaȝte (Kent), Middle English–1600s fourteth, 1500s fourtith, 1500s–1600s fortith, 1500s–1600s fourteth, 1500s–1600s fourtieth, 1500s– fortieth; also Scottish pre-1700 fourtid, pre-1700 fourtyde, pre-1700 fourtyid, pre-1700 fowrtyde; N.E.D (1897) also records a form late Middle English fortith.
β. Middle English fourtiand (northern).
γ. 1500s fourtyest.
Also represented by the abbreviations 40th, 40th, xlth, xlth, XLth, XLth, and variants.