• Aspect
• Lexical Modality
• Marginal Modal
• Modal
• Mood
• Stance
• Tense
• Toulmin Model

Etymology:

Examples and Observations:

• "[Modality] is a category that is closely associated with tense and aspect in that all three categories are categories of the clause and are generally, but not always, marked within the verbal complex.
  
  "In notional terms all three are, in some way, concerned with the event or situation that is reported by the utterance . . .. Tense, rather obviously, is concerned with the time of the event, while aspect is concerned with the nature of the event . . .. Modality is concerned with the status of the proposition that describes the event.
  
  "Modality differs from tense and aspect in that it does not refer directly to any characteristic of the event, but simply to the status of the proposition."
  (Frank Robert Palmer, Mood and Modality, 2nd ed. Cambridge Univ. Press, 2001)

• "[Modality] is what makes the difference between a factual assertion like unicorns never existed, and a more guarded view, such as it seems likely that unicorns could ever have existed--or a bolder claim like the existence of unicorns must always have been a myth. Modality, then, is a resource speakers and writers use when they are staking claims to knowledge: it allows them to formulate different kinds of claims (e.g., assertions, opinions, hypotheses, speculations) and indicate how committed they are to those claims."
  (Deborah Cameron, The Teacher's Guide to Grammar. Oxford Univ. Press, 2007)
• Types of Modality
  "Modality is concerned with the speaker's assessment of, or attitude towards, the potentiality of a state of affairs. Modality therefore relates to different worlds. Assessments of potentiality, as in You must be right, relate to the world of knowledge and reasoning. This type of modality is known as epistemic modality. Modal attitudes apply to the world of things and social interaction. This type of modality is known as root modality. Root modality comprises three subtypes: deontic modality, intrinsic modality and disposition modality. Deontic modality is concerned with the speaker's directive attitude towards an action to be carried out, as in the obligation You must go now. Intrinsic modality is concerned with potentialities arising from intrinsic qualities of a thing or circumstances, as in The meeting can be cancelled, i.e. 'it is possible for the meeting to be cancelled.' Disposition modality is concerned with a thing's or a person's intrinsic potential of being actualised; in particular abilities. Thus, when you have the ability to play the guitar you will potentially do so. Notions of modality are expressed by cognition verbs such as I think, modal adverbs such as possibly, and modal verbs such as must. Modal verbs have a special status among modal expressions: they ground a situation in potential reality."
  (Günter Radden and René Dirven, Cognitive English Grammar. John Benjamins, 2007)

• Examples of Modality Markers
  "The modality marker 'depth' is concerned with perspective, whose scale ranges from maximally deep perspective to the absence of depth. According to the naturalistic standard, the highest modality rests on the point along the scale that represents a central perspective, whereby objects far from the lens tend to reduce in size and the real-life parallel lines converge at a vanishing point within or outside the picture frame. Another modality marker that can be scaled is 'illumination,' which refers to the play of light and shade. The various degrees on this continuum range from the fullest representation of light and shade to its absence. Lastly, the modality marker 'brightness' is a scale that runs from a maximum number of degrees of brightness, to only the dark and light versions of a given colour."
  (Yumin Chen, "Contestable Reality: A Multi-Level View on Modality in Multimodal Pedagogic Context." Appliable Linguistics, ed. by Ahmar Mahboob and Naomi Knight. Continuuum, 2010)