Great means large in amount or degree.
(数量或程度) 大的 • Benjamin Britten did not live to a great age. 本杰明•布里滕没有活到很大的岁数。
You say great in order to emphasize that you are pleased or enthusiastic about something.
美妙的; 很棒的 • Oh great! That'll be good for Fred. 噢,太棒了!那对弗雷德将会很有利。
The greats in a particular subject or field of activity are the people who have been most successful or famous in it.
大人物 • ...all the greats of Hollywood. …所有的好莱坞名人。