Tense–aspect–mood (commonly abbreviated tam) or tense–modality–aspect

10
Tense–aspect–mood (commonly abbreviated tam) or tense–modality–aspect (abbreviated as tma) is a group of grammatical categories that are important to understanding spoken or written content, and which are marked in different ways by different languages.^[1]
TAM covers the expression of three major components of words which lead to or assist in the correct understanding of the speaker's meaning:^[2]

• 
  Tense—the position of the state or action in time, that is, whether it is in the past, present or future.
  
• 
  Aspect—the extension of the state or action in time, that is, whether it is unitary (perfective), continuous or repeated (imperfective).
  
• 
  Mood or Modality—the reality of the state or action, that is, whether it is actual (realis), a possibility or a necessity (irrealis).
  

For example, in English the word "walk" would be used in different ways for the different combinations of TAM:

• 
  Tense: He walked (past), He walks (present), He will walk (future).
  
• 
  Aspect: He walked (unitary), He was walking (continuous), He used to walk (repeated).
  
• 
  Mood: I can walk (possibility), Walk faster! (necessity).
  

In the last example, there is no difference in the articulation of the word, although it is being used in a different way, one for conveying information, the other for instructing.
In some languages, evidentiality (whether evidence exists for the statement, and if so what kind) and mirativity (surprise) may also be included. Therefore, some authors extend this term as tense–aspect–mood–evidentiality (tame in short).^[3]
Tense-mood-aspect conflation[edit]
The term was coined out of convenience,^{[by whom?]} for it is often difficult to untangle these features of a language. Several features (or categories) may be conveyed by a single grammatical construction (for instance, English -s is used for the third person singular present). However, this system may not be complete in that not all possible combinations may have an available construction. On the other hand, the same category may be expressed with multiple constructions. In other cases, there may not be delineated categories of tense and mood, or aspect and mood.
For instance, many Indo-European languages do not clearly distinguish tense from aspect.^{[4][5][6][7][8]}
In some languages, such as Spanish and Modern Greek, the imperfective aspect is fused with the past tense in a form traditionally called the imperfect. Other languages with distinct past imperfectives include Latin and Persian.
In the traditional grammatical description of some languages, including English, many Romance languages, and Greek and Latin, "tense" or the equivalent term in that language refers to a set of inflected or periphrastic verb forms that express a combination of tense, aspect, and mood.
In Spanish, the simple conditional (Spanish: condicional simple) is classified as one of the simple tenses (Spanish: tiempos simples), but is named for the mood (conditional) that it expresses. In Ancient Greek, the perfect tense (Ancient Greek: χρόνος παρακείμενος, romanized: khrónos parakeímenos)^[9] is a set of forms that express both present tense and perfect aspect (finite forms), or simply perfect aspect (non-finite forms).
However, not all languages conflate tense, aspect and mood. Some analytic languages such as creole languages have separate grammatical markers for tense, aspect, and/or mood, which comes close to the theoretical distinction.
Creoles[edit]
Creoles, both Atlantic and non-Atlantic, tend to share a large number of syntactic features, including the avoidance of bound morphemes. Tense, aspect, and mood are usually indicated with separate invariant pre-verbal auxiliaries. Typically the unmarked verb is used for either the timeless habitual or the stative aspect or the past perfective tense–aspect combination. In general creoles tend to put less emphasis on marking tense than on marking aspect. Typically aspectually unmarked stative verbs can be marked with the anterior tense, and non-statives, with or without the anterior marker, can optionally be marked for the progressive, habitual, or completive aspect or for the irrealis mood. In some creoles the anterior can be used to mark the counterfactual. When any of tense, aspect, and modality are specified, they are typically indicated separately with the invariant pre-verbal markers in the sequence anterior relative tense (prior to the time focused on), irrealis mode (conditional or future), non-punctual aspect.^{[10]: pp. 176–9, p. 191, [11]}