What is lexical phonology?

Definition
	Lexical phonology is an approach to phonology that accounts for the interactions of morphology and phonology in the word building process.
	The lexicon plays a central, productive role in the theory. It consists of ordered levels, which are the domain for certain phonological or morphological processes.

Discussion
	Here is a diagram of the overall structure of the lexical phonology model:

Components
	The following are crucial components of lexical phonology:
	Lexical and post-lexical rules Here is a table that compares lexical and post-lexical rules: Lexical rules … Post-lexical rules … Apply only within words. Apply within words or across word boundaries. Are prone to exceptions. Do not have exceptions. Require morphological information. Require syntactic information, or no grammatical information at all. Must be structure-preserving. Are not necessarily structure-preserving. Will not be blocked by pauses. Can be blocked by pauses. Apply first. Apply later. Levels English has between two and four levels of morphology in the lexicon. The levels within the lexicon are ordered so that, to get to Level 3 from Level 1, a word must pass through Level 2. A word cannot go back to a previous level once it has left one level and gone on to another level. Halle and Mohanan propose the following four levels of morphology in the lexicon: Level 1: Class 1 derivation, irregular inflection Level 2: Class 2 derivation Level 3: Compounding Level 4: Regular inflection We will consider the first two levels of affixation because they differ significantly. Here is a table that compares affixation on Levels 1 and 2: Level 1 Level 2 Affixes include: -ate, -ion, -ity, -ic, sub-, de-, in- Affixes include: -ly, -ful, -some, -ness, re-, un-, non- Affixation causes stress shift: photograph/photographic Affixation does not affect stress: revenge/revengeful Trisyllabic shortening occurs: divine/divinity No trisyllabic shortening occurs: leader/leaderless Nasal assimilation occurs: in + legal -> illegal Nasal assimilation is blocked: un + ladylike -> unladylike, not *ulladylike Affixes may attach to stems: re-mit, de-duce Affixes attach only to words: re-open, de-regulate Affixation is less productive and more exception ridden. Affixation is more productive and less exception ridden. Bracket erasure convention The bracket erasure convention is an important convention in lexical phonology. It ensures that the morphological brackets introduced within a certain level are erased before entering the next level. Example: Here is an example of the bracket erasure convention. The brackets in pressurize are erased before it enters Level II. Level I [press] [-ure] [-ize] +sfx [press] [-ure] +sfx [[[press] [-ure]] [-ize]] Level II [re-] [pressurize] (Bracket erasure) +pfx [[re-] [pressurize]]

Examples (English)
	Here is an example of an application of lexical phonology:
	Here are the words to be considered in this example: sane [sejn] / sanity [sQnIti] neighbor [nejb«&u0279;] / neighborhood [nejb«&u0279;hUd] *[nQb«&u0279;hUd]
	The following rule applies across level 1 morpheme boundaries: A tense vowel becomes lax when a short word is lengthened by adding a suffix, so that the words ends up having at least three syllables.
	This derivation demonstrates affixation in lexical phonology accompanied by the application of a phonological rule, trisyllabic shortening.