by reduplication of part of the stem (gukacha ‘s/he saw it’ vs guʼukacha ‘the two of them saw it’). Argument role Languages encode two main types of actions: those in which the main participant initiates an action that produces change in an object (e.g. kick a ball, buy a gift, cook a dish, read a book); and those in which the action produces no (perceived) change in the world or that have no object (sneezing, breathing, growing, diving, etc.). Actions that take an object are encoded by transitive verbs, whereas those that take no object are expressed via intransitive verbs. Intransitive verbs In Indo-European languages like English, all intransitive verbs behave similarly (‘They sneeze/breathe/dive/think’/etc.). In Keresan, actions that take no object are conceptualized in two distinct ways depending on how the initiator of the action is implicated. More active-like intransitive verbs (e.g. ‘to sneeze’) are coded through one set of morphemes, whereas actions conceptualized as involving the initiator at a lesser degree (e.g. ‘to believe’) are coded using a separate set of prefixes. Ideas expressed in Indo-European languages with adjectives are most often encoded by verbs in Keresan. That is, in Keresan one express the idea in the sentence ‘He is selfish’ by saying something along the lines of ‘He selfishes’. In such “actions”, the entity that is characterized by them is not implicated in the action directly (i.e. it's beyond their control), and thus belong in the Inactive intransitive category. The different sets of prefixes are shown below: Transitive verbs Aspect Aspect in Keresan is signalled by suffixes. Time (tense) adverbials The category of tense is expressed in Keresan via adverbs that indicate when the action about which one is speaking took place. Lexicon New words are coined through a number of roots that are combined to pre-existing ones. Compounding is a common strategy for word building, although derivation also occurs. Numerals The Keresan numeral system is a base 10 system. Numerals 11–19, as well as those between the multiple of tens, are formed by adding the word kʼátsi (/ kʼátsʰɪ / 'ten') followed by the word dzidra (/tsɪtʂa/ 'more'). Numerals 20 and above are formed by adding a multiplicative adverb (-wa or -ya) to the base number and the word kʼátsi. Loanwords from Spanish European colonizers arriving in the Southwest US brought with them material culture and concepts that were unknown to the peoples living in the area.