Ma'anar ƙamus na kalmar "shekarin tayi" yana nufin matakin girma na ɗan tayi a lokacin daukar ciki, yawanci ana aunawa a cikin makonni ko watanni tun farkon lokacin haila na ƙarshe (LMP) ko daukar ciki. An fi amfani da shi a cikin yanayin likita da na haihuwa don kwatanta shekarun haihuwa ko ci gaban tayin mai tasowa. Yawancin shekarun haihuwa ana amfani da su tare da shekarun haihuwa, kodayake a zahiri suna iya samun ɗan bambance-bambance dangane da hanyar lissafin da aka yi amfani da su.