Lines are strokes

STEMS
are the principal strokes, as in I or H (which has two), as has h, as even has y. Some people also call other things stems. You will not. For a generic expression you should use the word stroke, to differentiate it from a stem. You might also use the following expressions:

ARMS
are horizontal strokes, as in T, E and F. But they are also the upward sloping stroke in a K.

Even the whole of the finish at the top of the C is an arm. The little bit at the top, the upper part of the arm, however - as you will learn later - is a barb or a cat's ear.

BARS
are where you go to drown your sorrows. They are also the horizontal strokes that run into verticals in H and A.

e also has a bar, even if it is oblique, sloping slightly upwards, as in Venetian faces like Centaur. In that case you might call this a cross stroke, because people would know what you mean, but you shouldn't, because a

CROSS STROKE
is really open on at least one end as on t and f and Ð.

TAILS
you will expect that the dangly bit at the bottom of a Q would fit this description. You are right. But the strong diagonal stroke on K, k and R is also a tail

SPINES
These can be found on a porcupine, and on both S and s.