• Active Voice and Passive Voice
• Agent and Patient
• Causative Verb
• Intransitive Verb and Transitive Verb
• Pseudo-Passive
• Transitivity

Examples and Observations (Definition #1)

• "In the mid-20th century, grammarians devised the term ergative to describe a verb that can be used (1) in the active voice with a normal subject (actor) and object (the thing acted on) [I broke the window]; (2) in the passive voice, with the recipient of the verb's action as the subject of the sentence (and most often the actor's becoming the object of a by-phrase) [the window was broken by me]; or (3) in what one textbook called 'the third way,' active in form but passive in sense [the window broke]. Ergative verbs show remarkable versatility. For example, you might say that he is running the machine or the machine is running, she spun the top or the top spun, the crew decided to split the rail or the rail split at that point."
  (Bryan Garner, Garner's Modern American Usage. Oxford University Press, 2009)

• Ergative Pairs
  "When the Affected object of a transitive clause (e.g. the bell) is the same as the Affected subject of an intransitive clause, we have an ergative alternation or ergative pair, as in I rang the bell (transitive) and the bell rang (intransitive). . . . English marks both the subject of an intransitive clause and that of an intransitive clause as nominative, and the object of the transitive as accusative. We can see this in the two meanings of leave: he left (went away, intrans.), he left them (abandon trans.). . . .
  
  Ergative pairs account for many of the most commonly used verbs in English, some of which are listed below, with examples:

  burn I've burned the toast. The toast has burned.
  break The wind broke the branches. The branches broke.
  burst She burst the balloon. The balloon burst.
  close He closed his eyes. His eyes closed.
  cook I'm cooking the rice. The rice is cooking.
  fade The sun has faded the carpet. The carpet has faded.
  freeze The low temperature has frozen the milk. The milk has frozen.
  melt The heat has melted the ice. The ice has melted.
  run Tim is running the bathwater. The bathwater is running.
  stretch I stretched the elastic. The elastic stretched.
  tighten He tightened the rope. The rope tightened.
  wave Someone waved a flag. A flag waved.

  Within this alteration--described here as an 'ergative pair'--there is a set of basically intransitive volitional activities (walk, jump, march) in which the second participant is involved either willingly or unwillingly. The control exerted by the Agent predominates in the causative-transitive:

  He walked the dogs in the park. The dogs walked.
  He jumped the horse over the fence. The horse jumped over a fence.
  The sergeant marched the soldiers. The soldiers marched.

  It is also possible to have an additional agent and an additional causative verb in the transitive clauses of ergative pairs; for example, The child got his sister to ring the bell, Mary made Peter boil the water."
  (Angela Downing and Philip Locke, English Grammar: A University Course. Routledge, 2006)
• The Difference Between Transitive Processes and Ergative Processes
  "What distinguishes a transitive from an ergative process? Characteristic of transitive processes (e.g., chase, hit, kill) is that they are Actor-centered: their 'most central participant' is the Actor, and the 'Actor-Process complex is grammatically more nuclear and relatively more independent' ([Kristin] Davidse 1992b: 100). The basic Actor-Process complex can be extended only to include a Goal, as in The lion is chasing the tourist. Ergative processes such as break, open and roll, in contrast, are 'Medium-centered,' with the Medium as 'most nuclear participant' (Davidse 1992b: 110) (e.g., The glass broke). The basic Medium-Process constellation can only be opened up to include an Instigator, as in The cat broke the glass. While the transitive Goal is a 'totally "inert" Affected,' the ergative Medium 'co-participates in the process' (Davidse 1992b: 118). In ergative one-participant constructions such as The glass broke, this active coparticipation of the Medium in the process is foregrounded and the Medium is presented as 'semi-' or 'quasi-autonomous' (Davidse 1998b)."
  (Liesbet Heyvaert, A Cognitive-Functional Approach to Nominalization in English. Mouton de Gruyter, 2003)

Examples and Observations (Definition #2): Ergative Languages and Nominative Languages

• "An ergative language is one in which the subject of an intransitive verb (e.g., 'Elmo' in 'Elmo runs home') is treated in grammatical terms (word order, morphological marking) similarly to the patient of a transitive verb (e.g., 'Bert' in 'Elmo hits Bert') and differently from the agent of a transitive verb ('Elmo' in 'Elmo hits Bert'). Ergative languages contrast with nominative languages such as English; in English, both the subject of the intransitive verb ('Elmo runs home') and the agent of a transitive verb ('Elmo hits Bert') are placed before the verb, whereas the patient of a transitive verb is placed after the verb ('Elmo hits Bert')."
  (Susan Goldin-Meadow, "Language Acquisition Theories." Language, Memory, and Cognition in Infancy and Early Childhood, ed. by Janette B. Benson and Marshall M. Haith. Academic Press, 2009)
• "In English, for example, the grammar in the two sentences Helen opened the door and The door opened is quite different, though the agency of the event might be thought of as being the same. A language with an ergative case would articulate these relationships very differently. Examples of ergative languages include Basque, Inuit, Kurdish, Tagalog, Tibetan and many native Australian languages like Dyirbal."
  (Robert Lawrence Trask and Peter Stockwell, Language and Linguistics: The Key Concepts, 2nd ed. Routledge, 2007)
• "[E]rgativity is a recessive feature (Nichols 1993), that is, a feature which is almost always lost by at least some daughter languages in a family and is not readily borrowed in contact situations. Thus, though not always inherited, when found in a language it is more likely to have been inherited than borrowed. Therefore, ergativity can be an important component of the grammatical signature of a language family: not every daughter language has it, but its mere presence in several or most languages of the family helps characterize the family and identify languages belonging to the family."
  (Johanna Nichols, "Diversity and Stability in Language." The Handbook of Historical Linguistics, ed. by Brian D. Joseph and Richard D. Janda. Blackwell, 2003)