Definitions

The following definitions are given as an aide-mémoire; they are not eternal truths, but need to be supported by evidence and argument.

1. We define form as the phonological (or orthographic) shape of a unit of language such as a word or part of a word. The form is sometimes called the realisation or the exponent of the unit of language.
2. We define a category as a class of linguistic units with similar distributions, i.e. which occur in similar contexts. A syntactic category is a class of words which occur in similar syntactic contexts. A category is also known as a part of speech, abbreviated POS.
3. We assume the basic type of linguistic unit to be the word, which is constituted of smaller parts (such as simpler words, stems, affixes), and which occurs in larger contexts (such as phrases, sentences, texts).
4. We define a meaning as the relation between a linguistic unit and the world, whereby `the world' may be understood in different ways - as objects, as concepts, as thoughts, ...
5. We define morphosemantics as the relation between the categories of words and their meanings.
6. We define morphophonology as the relation between the categories of words and their phonological forms.
7. We define morphorthography as the relation between the categories of words and their orthographic forms.
8. We define morphotactics as the compositional relation between the parts of words.
9. We define inflection as the branch of morphotactics concerned with the marking of relations between words and their syntactic and situational contexts.
10. We define word formation as the branch of morphotactics concerned with the recursive construction of complex words from simpler words and/or affixes (here designed specifically for the main aspects of English morphotactics):
    1. Derivation:
       1. A root is a verb, noun or adjective morpheme.
       2. An inflection is an inflectional suffix.
       3. A derivation is a root, or a derivation with a derivational affix.
       4. A derivation head is a root, or a derivation suffix.
       5. An inflected derivation head is a derivation head (the modifier) concatenated with an inflection (the head).
       6. An inflected derivation is an inflected root or a derivation (the modifier) concatenated with an inflected derivation head (the head).
    2. Word:
       1. A word is an inflected root or a derivation (the modifier) terminated by an inflected derivation head (the head).
    3. Compound:
       1. A compound is a word, or a derivation (the modifier) concatenated with a compound (the head).

Note that fairly arbitrary items may be modifiers in compounds, such as `rank shifted' compounds, such as phrasal compounds: `A sit-down-and-relax invitation.'