The present paper is an introduction to unification as a formalism for writing grammars for natural languages. The paper is structured as follows. Section 1 briefly describes the history and the current scene of unification based grammar formalisms. Sections 2–3 describe the basic design of current formalisms. Section 4 constitutes a tutorial introduction to a representative unification based grammar formalism, the D–PATR system of Karttunen (1986). Sections 5—6 consider extensions of the unification formalism and its limitations. Section 7 examines implementation questions and addresses the question of the computational complexity of unification. — Some notes on terminology.

This paper discusses variation in liguistic change on the basis of the distribution of apocope in Central Norway. The results of a detailed study of the dialect of Oppdal, which are compared with studies on variation in linguistic change in other languages, show that the diffusion of morphophonological innovations may depend on various linguistic as well as extra-linguistic factors. The investigation seems to support the hypothesis that there is no basic difference between the mechanisms of system-internal change and change produced by external influence.

The present paper makes a case for retention of the (Revised) Alternation Condition in Lexical Phonology, a theory in which any single rule which presebts beytralizing, lexical effects restricted to derived forms along with allophonic, derivationally unterstricted dffects is cominally impossible. However, Korean obstruent palatalization does display both of these properties, whereby /t, th/ neutralize with /ĉ, ĉh/ before [i], but only if the [i] occurs in another morpheme (cf. /path + i/→ [paĉhi] ‘field-SUBJ’ vs. monomorphemic [pathi] ‘endure’), whereas / s / acquires the palatal allophone [∫[ before [i] both within ([∫i] ‘poem’) and between (/os + i/→ [o∫i] ‘cloth-SUBJ’) morphemes. The Revised Alternation Condition alone imposes just this restriction on a single palatalization rule functioning both lexically and post-lexically in Korean, which suggests that its removal from the theory is premature.

As pointed out by numerous researchers, only a limited degree of correspondence exists between Polish and Swedish concerning the use of tense and aspect. The discrepancies lead to several typical interference phenomena in Polish speakers learning Swedish. This article contains a contrastive analysis of forms and functions of tense and aspect in Polish and Swedish, where the main sources of interference phenomena are pointed out.

Bound neuter i-stems in Modern Icelandic, which occur as heads of compounds in for example salanguryroi ‘slang word’, support an overgenerating model of the lexicon. Bound stems are shown to be generated as constituents at level 1 of the lexicon and combined to form compounds at level 2. Bound stems are blocked from becoming inputs to the syntax by the Avoid Synonymy principle (Kiparsky 1983), revised as a constraint on the output of the lexicon as a whole. Because Avoid Synonymy operates in lexical Logical Form, it has access to word-internal structure at each lexical level. The revised version of Avoid Synonymy is given additional support from Icelandic and English.