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Morphemic Tier Hypothesis (MTH)

PHONOLOGY/MORPHOLOGY: a hypothesis first introduced into the theory of Autosegmental phonology in McCarthy (1981) which entails the claim that every morpheme making up a word is assigned a separate tier, i.e., a separate and autonomous level of representation. This hypothesis is mainly proposed to circumvent the No-Crossing Constraint which says that association lines may not cross. EXAMPLE: the Arabic word katab is made out of the triliteral root ktb 'write', the perfective active morpheme a, and the template CVCVC. If the morphemes ktb and a were represented at a single tier, association of these morphemes to the template CVCVC would result in a violation of the No-Crossing Constraint, as is shown in (i). By representing them at autonomous tiers as in (ii), this problem is solved:

 (i) *	C V C V	C	* C V C V C
        | | |   |         |   |   |
	k a t	b	  k   t   b  a

(ii)	    a
           / \
	C V C V	C
        |   |   |
	k   t	b

LIT. Goldsmith, J. (1990)
McCarthy, J. (1986)
McCarthy, J. (1981)
Spencer, A. (1991)