In next years, it is necessary to draft and adopt thousands of standards and other normative documents identical to the European ones. This makes it important to formulate and adopt clear and unambiguous rules for drafting these documents. These rules should fully meet the norms of the modern Ukrainian language. One of the problems is related to the usage rules for verbs with affixes -sia (hereinafter referred to as the sia-verbs), which represent about a third (33%) of the total number of Ukrainian verbs. The essence of the problem with these verbs is that under the influence of the Russian language sia-verbs are widely used in passive constructions, which, according to leading Ukrainian linguists, don’t meet the norms of the modern Ukrainian language. The problem with these verbs is that under the influence of the Russian language sia-verbs are still widely used in passive constructions, which, according to leading Ukrainian linguists, don’t meet the norms of the modern Ukrainian language. The purpose of this article is to suggest consistent terms and definitions of basic concepts, which are needed to draft these rules, and clear criteria that would allow clearly distinguish inherent Ukrainian constructions from intruded ones. In the article, the terms for denoting verbs with affixes –sia are analysed and the advantages of the term “sia-verb” over other terms are shown. The confusion behind the usage of the terms “process” and “action”, which are very important for the formulation of rules, is investigated. It is suggested to use the term “process” as a generic term denoting the categorical meaning of the verb as parts of speech, regardless of the specific lexical meanings of an individual verb, and to use the term “action” as specific term denoting the kind of process, which is generated and directly stimulated by a logical subject. It is noted that using these terms for denotation of other concepts is inappropriate, because it can lead to confusion. The difference is shown between the transitivity/intransitivity of a process as a semantic concept and the transitivity/intransitivity of verbs that name these processes. In semantics, the criterion of process transitivity is the direction of the process and its extension to a logical object other that the logical subject. Classification of verbs by transitivity is solely based on a formally morphological criterion associated with a grammatical object, which may or may not be required by the verb used in a certain meaning. Examples are given, which demonstrate that the semantic and grammatical approaches to transitivity do not always match. It is shown that for sia-verbs, the main and primary meaning is the reflexive one (broadly speaking, this is the meaning of an intransitive process, which is focused, looped within the realm of the logical subject that, at the same time, can be the logical object). There have been selected nine sub-meanings of the reflexive meaning, that convey different shades of reflexivety – from processes focused on the logical subject to the processes having a very wide general relation to it, including ones that convey permanent and defining intransitive possessive abilities (properties). The names for these sub-meanings present in the literature have been analyzed and a consistent system of Ukrainian terms is suggested for them. These terms are built based on a pattern, which, on the one hand, makes these specific concepts’ relation with the generic concept “reverse meaning” obvious thanks to the generic characteristic, and, on the other hand, explicitly shows the difference of every specific concept from other subordinate concepts via their delimiting characteristics. Five of these terms are generally accepted, one is chosen from the options available in the literature, but three more terms are suggested from the scratch to meet the requirement of being systematic. Thereby, the Ukrainian language naturally uses the sia-verb in the situations, where the speaker treats the process as intransitive one, i.e. there is no logical subject separated from the logical object. Therefore intransitivity / transitivity of processes is the criterion that makes it possible to distinguish inherent Ukrainian reflexive and impersonal constructions from intruded ones.