You could argue that "B", "D" and lowercase "t" also have perpendicular lines but they are not straight lines so I don't know if those count.
W
T p h
Parallel: E, F, H, I, M, N, O (in some fonts), U, Z. Perpendicular: E, F, G, H, L, T. Many more letters have perpendicular lines in serif fonts. Also, there are letters, such as D, in which the ends of the curved section are parallel to one another and are perpendicular to the vertical element.
There are letters in the alphabet with both parallel and perpendicular lines. In alphabetical order, they are E, F, and H. If the joining point can be considered perpendicular and parallel, then B, D, P, and R also match the criterion.
The letter's "H", "I", "E", and "F".
Yellow
W
T p h
t
M
Parallel: E, F, H, I, M, N, O (in some fonts), U, Z. Perpendicular: E, F, G, H, L, T. Many more letters have perpendicular lines in serif fonts. Also, there are letters, such as D, in which the ends of the curved section are parallel to one another and are perpendicular to the vertical element.
There are letters in the alphabet with both parallel and perpendicular lines. In alphabetical order, they are E, F, and H. If the joining point can be considered perpendicular and parallel, then B, D, P, and R also match the criterion.
E F and H
The letters A, K, M, N, R, V, W, Y, and Z all have lines in them that are not perpendicular.
The letter's "H", "I", "E", and "F".
N, M and H
Perpendicular lines are ones that make right angles when they meet. For instance the letters T H E and L are all made of perpendicular line segments.