type terminology lexicon from a type primer, John Cane, Prentice Hall, 2003:
Baseline-The imaginary line defining the visual base of the letterforms.
Median-The imaginary line define the x-height of the letterforms.
X-height-The height in any typeface of the lowercase 'x'.
Stroke-Any line that defines the basic letterform.
Apex/Vertex-The point created by joining two diagonal stems(apex above, vertex below).
Arm-Short strokes off the stem of the letterform.
Ascender-The portion of the stem of a lowercase letterform that projects above the median.
Barb-The half-serif finish on some curved strokes.
Beak-The half-serif finish on some horizontal arms.
Bowl-The rounded form that describes a counter. The bowl may be either open or closed.
Bracket-The transition between the serif and the stem
Counter-The negative space within a letterform, either fully or partially closed.
Cross Bar-The horizontal stroke in a letterform that joins two stems together.
Cross Stroke-The horizontal stroke in a letterform that intersects the stem
Crotch-The interior space where two strokes meet
Descender-The portion of a stem of a lowercase letterform that projects below the baseline
Ear-The stroke extending out from the main stem or body of the letterform.
Em/en-Originally referring to the width of an uppercase M, an em is now the distance equal to the size of the typeface(an em in 48 pt. type is 48 points) An en is half the size of an em.
Finial-The rounded non-serif terminal to a stroke.
Leg-Short stroke off the stem of the letterform, either at the bottom of the stroke or inclined downward.
Ligature-The character formed by the combination of two or more letterforms.
Link-The stroke that connects the bowl and the loop.
Loop-The bowl created in the descender of the lowercase G.
Serif-The right angled or oblique foot at the end of the stroke.
Shoulder-The curved stroke that is not part of a bowl.
Spine-The curved stem of the S.
Spur-The extension that articulates the junction of a curved and rectilinear stroke.
Stem-The significant vertical or oblique stroke.
Stress-The orientation of the letterform, indicated by the thin stroke in round forms.
Swash-The flourish that extends of the stroke of a letterform.
Tail-The curved or diagonal stroke at the finish if certain letterforms.
Terminal-The self-contained finish of a stroke without a serif, a catch-all term.