Perfective verbs have a simple future tense (formed like the present tense of imperfective verbs), past tense, subjunctive/conditional, imperatives, infinitive, present gerund and past participle. Conjugated verb forms agree with their subject in terms of person, number, and (in the case of past tense and subjunctive/conditional forms) gender. Passive-type constructions can be made using the auxiliary "być" or "zostać" ("become") with the passive participle. There is also an impersonal construction where the active verb is used (in third person singular) with no subject, but with the reflexive pronoun "się" present to indicate a general, unspecified subject (as in "pije się wódkę" "vodka is being drunk"—note that "wódka" appears in the accusative). A similar sentence type in the past tense uses the passive participle with the ending "-o", as in "widziano ludzi" ("people were seen"). As in other Slavic languages, there are also subjectless sentences formed using such words as "można" ("it is possible") together with an infinitive. Yes-no questions (both direct and indirect) are formed by placing the word "czy" at the start. Negation uses the word "nie", before the verb or other item being negated; "nie" is still added before the verb even if the sentence also contains other negatives such as "nigdy" ("never") or "nic" ("nothing"), effectively creating a double negative. Cardinal numbers have a complex system of inflection and agreement. Zero and cardinal numbers higher than five (except for those ending with the digit 2, 3 or 4 but not ending with 12, 13 or 14) govern the genitive case rather than the nominative or accusative. Special forms of numbers (collective numerals) are used with certain classes of noun, which include "dziecko" ("child") and exclusively plural nouns such as "drzwi" ("door"). Polish has, over the centuries, borrowed a number of words from other languages. When borrowing, pronunciation was adapted to Polish phonemes and spelling was altered to match Polish orthography. In addition, word endings are liberally applied to almost any word to produce verbs, nouns, adjectives, as well as adding the appropriate endings for cases of nouns, adjectives, diminutives, double-diminutives, augmentatives, etc.  Depending on the historical period, borrowing has proceeded from various languages.