The leaves of green and Oolong-teas are usually whole and the grade is not specified. The same applies for a few of the black teas, esp Chinese, where its name stands for quality. For other black teas the grade is important since it gives info about the fineness of the crop, and the size of the leaf (whole, broken, ground).
In these grading the term "orange" is not connected with the fruit of the same name. It means "royal", and comes from the name of the Dutch dynasty Orange Nassau. As for the word Pekoe comes from the Chinese word Pak-ho meaning "fine hair" or "down", and denotes the end bud, which gives an impression of white down
▪ F.O.P. Flowery Orange Pekoe
Finest crop of all. Composed of the final bud and the following two leaves. The tea contains many buds that, after been browned during fermentation, are sometimes known as "golden tips".
▪ O.P. Orange Pekoe
Young, tightly rolled leaves. The crop is fine but a little later than the above: in this case the bud has already become a leaf
▪ P. Pekoe
The leaf is less fine than the O.P. and does not contain any buds
▪ S. Souchong
Leaves are lower, larger, older and with a lower caffeine content; often rolled lengthwise and are used for smoked teas
The leaf is no longer whole
Much smaller than the O.P.
An infusion of this tea gives a much darker, stronger beverage.
▪ B.O.P. Broken Orange Pekoe
▪ F.B.O.P. Flowery B.O.P.
▪ G.B.O.P. Golden B.O.P.
▪ T.G.B.O.P. Tippy Golden B.O.P.
▪ F. Fannings
Flat pieces smaller than broken leaves.
The infusion produced is very strong and highly coloured
Leaves not yet ground, mainly used for tea bags
▪ G.F.O.P. Golden Flowery Orange Pekoe
F.O.P. has a high proportion of buds
▪ T.G.F.O.P. Tippy Golden Flowery Orange Pekoe
F.O.P. containing many golden buds
▪ F.T.G.F.O.P. Finest Tippy Golden Flowery Orange Pekoe
F.O.P. of exceptional quality
▪ S.F.T.G.F.O.P. Special Finest Tippy Golden Flowery Orange Pekoe
F.O.P. of the finest exceptional quality
A grade usually reserved for the best springtime Darjeelings