definitions.

absolute measurement-measurements of fixed values; all absolute measurements are expressed in finite terms that cannot be altered

relative measurement-many measurements, such as character spacing, are linked to type size, which means the relationships are defined by a series of relative measurements; ems and ens are examples of relative measurements that have no prescribed, absolute size; their size is relative to the size of the type being set

points-the point is the unit of measurement used to measure the type size of a font (ex: 7pt Times New Roman); this measurement refers to the height of the typed block, not the letter itself; also 1/72nd of an inch

picas-unit of measurement equal to 12 points that is commonly used for lines of type

x-height-the height of the lowercase 'x'; as such is a relative measurement that varies from typeface to typeface

the em-a relative unit of measurement used in typesetting to define basic spacing functions, and therefore it is linked to the size of the type; equals the size of the given type

the en-a unit of relative measurement equal to half of one em

en dash- 1/2 of an em rule and is used to separate page numbers, dates, and to replace the word 'to' in construction implying movement

em dash- used to form lines and house nested clauses

hyphen-1/3 of an em rule and is used to link words

alignment-refers to the position of type within a text block, in both the vertical and horizontal planes

justification-this alignment allows the appearance of rivers of white space to appear;  word spacing on separate lines is irregular, unlike range left type where all lines have the same spacing

flush left-this alignment follows the principle of handwriting, with text tight and aligned to the left margin and ending ragged on the right

flush right-right aligning text is less common as it is more difficult to read;  it is sometimes used for picture captions and other accompanying texts as it is clearly distinct from body copy

letterspacing-adds space between letterforms to open up text;  the addition of too much space can make text look disjointed as words start to dissemble

kerning-the removal of space between characters;  kern originally referred to part of a character that extended outside its bounding block or printing block

tracking-adjusting this affects the amount of spacing between characters

word spacing-adjusts the amount of space between words

widow-lone word at the end of a paragraph

orphan-the final one or two lines of a paragraph separated from the main paragraph to form a new column, and should be avoided at all costs

leading-a hot-metal printing term that refers to the strips of lead that were inserted between text measures in order to space them accurately; leading is specified in points and refers nowadays to the space between lines of text in a text block

indent-text blocks can be indented so that some or all of the text lines are moved in from the margin by a specified amount; traditionally the first paragraph is not indented, with indentation commencing with the second paragraph

first line indent-the text is indented from the left margin in the first line of the second and subsequent paragraphs;  the first paragraph in a document following a heading, subhead, or crosshead is not normally indented as this introduces an awkward space, although this can be done

hanging indent-similar to a running indent except the first line of the text is not indented