Purpose sentences describe a relationship of two events, in which the main event must occur in order to allow the second, also known as the purpose event. In this type of sentence, the phrase or clause describing the purpose event is called the purpose construction. This construction may be either (a) a finite or nonfinite verb form (purpose complement), or (b) a clause (purpose clause).
This parameter considers whether the form in which a verb appears in a purpose construction differs from that of an independent clause.[1] If the two verb forms appear in the same form, the indirect verb form is termed balanced (Bal); if not, it is considered special or deranked (Drk).[2] In the majority of languages, either a special form or base form must appear obligatorily, the latter being the significantly more frequent option.[3] The form of the verb may depend on whether the purpose construction has the same or different subject than the main clause[4], or on grammatical features of the verb such as transitivity and verbal class.
Types:
PurpVBal: The verb of a purpose construction obligatorily appears in base form.[5]
PurpVBalSameSbj: The verb of a purpose construction appears in base form if the subject of the purpose construction is coreferential with that of the main clause; otherwise, a special form is used.[6]
PurpVBalDiffSbj: The verb of a purpose construction appears in base form if the subject of the purpose construction is not coreferential with that of the main clause; otherwise, a special form is used.
PurpVBalDiffV: The verb of a purpose construction can appear in either base form or a special form, depending on the grammatical features of the verb[7].
PurpVDrk: The verb of a purpose construction always appears in a single special form, regardless of both the features of the verb and whether the subject of the purpose construction is coreferential with that of the main clause.
PurpVDrkDiffV: The verb of a purpose construction always appears in a special form, regardless of whether the subject of the purpose construction is coreferential with that of the main clause; however, the specific special form in which it appears (or can appear) depends on the features of the verb.[8]
PurpVDrkDiffSbj: The verb of a purpose construction always appears in a special form; however, the specific special form in which it appears (or can appear) depends on whether the subject of the purpose construction is coreferential with that of the main clause.
When a language displays more than one strategy, two values can be listed. If one strategy is dominant, a slash (/) can separate the two values, with the dominant value appearing first; if neither is dominant, they are listed with an ampersand (&) separating the two. The use of parentheses indicates that use of the strategy is not obligatory. Explanation and examples should be included.
[1] If the difference between the purpose construction and the independent verb form is that the purpose construction has a special affix or clitic, and its removal would result in the form used in an independent clause, then the two verb forms are considered to be the same, since the affix functions as a conjunction marking the structure as a purpose construction.
[2] Special or “demoted” verb forms include nonfinite verb forms and verb forms that differ from the base form in their tense, aspect, mood, person marking, case marking, or co-occurrence with adpositions. Examples include infinitives and the subjunctive. These verb forms may also fulfill other functions in the language, in addition to their role in purpose constructions.
[3] The commentary should specify whether use is obligatory or optional.
[4] For example, a language may use a different structure to express the sentence I went there to show her my collection (I went, I showed) than in the sentence I went there so she could show me her collection (I went, she showed).
[5] This value also includes languages that do not grammatically mark purpose constructions. In such languages, the function must be inferred logically or based on contextual cues.
[6] Special form refers to the special form of either a finite or nonfinite verb.
[7] Grammatical features may include inflectional types, meaning, etc.
[8] “Appears” refers to obligatory use, whereas “can appear” refers to optional use. Although the parameter value applies equally to both types, it should be specified in the commentary whether use is obligatory or optional.