Glossary A

Apraxia refers to the loss of a previously acquired ability to perform purposeful movements in response to verbal commands.

Aptitude refers to one's capability or potential for performing a particular task or skill or for learning a specific skill; usually involves a narrower skill than ability (examples are: mathematics aptitude, musical aptitude or foreign language aptitude).

- Aptitude-treatment interaction: - Aptitude-treatment interaction (ATI) : Aptitude-treatment interaction (ATI) refers to a phenomenon whereby characteristics of the student and of the school environment interact to affect student outcomes, such that any given educational practice may be effective with some students but not with others

- AQS (Attachment Q-set) : AQS or Attachment Q-set refers to alternative method of assessing attachment security that is based on observations of the child’s attachment-related behaviors at home which can be used with infants, toddlers, and preschool children.

Arachnoid granulations refer to small "pockets" of cauliflower-like veins within the sub-arachnoid space, which serve as pathways for the sub-arachnoid cerebrospinal fluid to be absorbed and re-enter the venous circulation.
Arachnoid membrane refers to a "spiderlike" avascular membrane of the meninges.

Arachnophobia refers to an abnormal and persistent fear of spiders. Sufferers from arachnophobia experience undue anxiety even though they realize the risk of encountering a spider and being harmed by it is small or nonexistent. They may avoid going barefoot and may be especially alert when taking showers or getting into and out of bed. This phobia was exploited in a 1990 movie called Arachnophobia.

Arbitrariness refers to the fact that a word is not inherently related to the concept it represents. Arbitrariness is a feature of language in which there is no direct resemblance between words and their referents.