According to the most common analysis, Otomi has two kinds of bound morphemes, proclitics and affixes. Proclitics differ from affixes mainly in their phonological characteristics; they are marked for tone and block nasal harmony. Some authors consider proclitics to be better analyzed as prefixes. The standard orthography writes proclitics as separate words, whereas affixes are written joined to their host root. Most affixes are suffixes and with few exceptions occur only on verbs, whereas the proclitics occur both in nominal and verbal paradigms. Proclitics mark the categories of definiteness and number, person, negation, tense and aspect - often fused in a single proclitic. Suffixes mark direct and indirect objects as well as clusivity (the distinction between inclusive and exclusive "we"), number, location and affective emphasis. Historically, as in other Oto-Manguean languages, the basic word order is Verb Subject Object, but some dialects tend towards Subject Verb Object word order, probably under the influence of Spanish. Possessive constructions use the order "possessed-possessor", but modificational constructions use "modifier-head" order.