paradigm, giving paradigms with three underlying grades. Another extremely important feature of Estonian gradation is that, due to the greater loss of word-final segments (both consonants and vowels), the Estonian gradation is an almost entirely opaque process, where the consonant grade (short, long, or overlong) must be listed for each class of wordform. So, for example, 'embrace' has the same form for all cases (e.g. genitive ), while hammas 'tooth' has weak grade mm in the nominative hammas and partitive hammast, but strong form mb in the genitive hamba and all other cases of the singular. There is a large number of cases in which inflectional endings are identical except for how they affect the consonant grade, e.g. leht 'leaf' belongs to a declension class in which both the genitive and the partitive singular are formed by adding -e, but the genitive takes the weak form (leh-e), while the partitive takes the strong form (leht-e). In the end, the types of generalizations that can be made are that some inflectional categories always take the strong form (e.g. partitive plural, -ma infinitive), some always take the weak form (e.g. -tud participle), some forms may take the overlong form (some partitive singulars, short illative singular), while other inflectional categories are underdetermined for whether they occur with weak or strong grade. In this last case, within a paradigm some forms are constrained to have the same grade and others are constrained to have the opposite grade; thus all present tense forms for the same verb have the same grade, though some verbs have strong (hakkan 'I begin', hakkad 'you begin', etc.) and others have weak ( 'I read', , 'you read', etc.), and the -da infinitive has the opposite grade from the present (hakata 'to begin', lugeda 'to read'). The system of gradation has also expanded to include gradation of all consonant clusters and geminate consonants (generally quantitative), when occurring after short vowels, and vowel gradation between long and overlong vowels, although these are not written except for the distinction between voiceless stops and geminate voiceless stops (e.g. overlong strong grade tt with weak grade t). E.g. linn , 'city (nom.)' vs. linna 'city (gen.)'. In consonant clusters, in the strong grade the first consonant is lengthened, e.g. must , 'black (nom.)' vs. musta 'black (gen.)'. Before single consonants, long vowels and diphthongs also become overlong in strong forms and remain merely long