From wiktionary:
memory (countable and uncountable; plural memories)

  1. The ability of an organism to record information about things or events in the brain with the facility of recalling them later at will.
    Memory is a facility common to all animals.
  2. A record of a thing or an event stored in the brain of an organism.
    I have no memory of that event.

And from wikipedia:

Memory is the ability of the brain to store, retain, and subsequently recall information. Although traditional studies of memory began in the realms of philosophy, the late nineteenth and early twentieth century put memory within the paradigms of cognitive psychology. In the recent decades, it has become one of the principal pillars of a new branch of science that represents a marriage between cognitive psychology and neuroscience, called cognitive neuroscience.

There are several ways of classifying memories, based on duration, nature and retrieval of information. From an information processing perspective there are three main stages in the formation and retrieval of memory:

  • Encoding (processing and combining of received information)
  • Storage (creation of a permanent record of the encoded information)
  • Retrieval/Recall (calling back the stored information in response to some cue for use in some process or activity)

>and a quote: “Memory is but the storage of fragmentary but ‘relevant’ features” – Walter J. Ong
Read on for selections from the OED definition…

Oxford English Dictionary:
memory, n.

I. Senses relating to the action or process of commemorating, recollecting, or remembering.

3. a. The perpetuated knowledge or recollection (of something;that which is remembered of a person, object, or event; (good or bad) posthumous reputation.

4. a. The length of time over which the recollection of a person or a number of persons extends. Chiefly in beyond (also past, out of) (the) memory (of____); similarly within memory, etc. through all memory: for all time (obs.).

5. The fact or condition of being remembered. Now somewhat arch.

II. Senses relating to the faculty of recalling to mind.

6. a. The faculty by which things are remembered; the capacity for retaining, perpetuating, or reviving the thought of things past.

d. The capacity of a body or substance for manifesting effects of, or exhibiting behaviour dependent on, its previous state, behaviour, or treatment; such effects; a state manifesting this capacity. Freq. with conscious metaphor.

7. a. The faculty by which things are remembered considered as residing in the awareness or consciousness of a particular individual or group. Freq. with preceding word or other contextual indication of the extent to which the faculty is developed or the field in which it is most active (cf. sense 6c).