Definitions of schema on the Web:

• an internal representation of the world; an organization of concepts and actions that can be revised by new information about the world
• outline: a schematic or preliminary plan
  wordnetweb.princeton.edu/perl/webwn

• A schema (pl. schemata), in psychology and cognitive science is: * A mental structure that represents some aspect of the world. * A structured cluster of pre-conceived ideas. * An organized pattern of thought or behavior. * A specific knowledge structure or cognitive representation of the self. ...
  en.wikipedia.org/wiki/Schema_(psychology)

• In Kantian philosophy, a schema (plural: schemata) is the procedural rule by which a category or pure, non-empirical concept is associated with a mental image of an object. It is supposedly produced by the imagination through the pure form of time.
  en.wikipedia.org/wiki/Schema_(Kant)

• SCHEMA is a computational algorithm used in protein engineering to identify fragments of proteins (called schemas) that can be recombined without disturbing the integrity of the proteins' three-dimensional structure. ...
  en.wikipedia.org/wiki/SCHEMA_(bioinformatics)

• In computer science, in the field of genetic algorithms, a schema is a template that identifies a subset of strings with similarities at certain string positions. Schemata are a special case of cylinder sets; and so form a topological space.
  en.wikipedia.org/wiki/Schema_(genetic_algorithms)

• In mathematical logic, an axiom schema (plural: axiom schemata) generalizes the notion of axiom.
  en.wikipedia.org/wiki/Schema_(logic)

• The degrees of Eastern Orthodox monasticism are the stages an Eastern Orthodox monk or nun passes through in their religious vocation.
  en.wikipedia.org/wiki/Schema_(Orthodoxy)

• The schema (pronounced skee-ma) of a database system is its structure described in a formal language supported by the database management system (DBMS). ...
  en.wikipedia.org/wiki/Schema_(database)

• An outline or image universally applicable to a general conception, under which it is likely to be presented to the mind; A formal description of the structure of a database: the names of the tables, the names of the columns of each table, and the type and other attributes of each column. ...
  en.wiktionary.org/wiki/schema

• in markup, a set of rules for document structure and content.
  scripts.sil.org/cms/scripts/page.php

• In general terms, any organization, coding, outline or plan of concepts. In terms of metadata, a systematic, orderly combination of elements or terms. ...
  dublincore.org/groups/tools/glossary.shtml

• A document that describes an XML or RDF vocabulary. Any document which describes, in formal way, a language or parameters of a langauge. The RDF Schema
  www.w3.org/People/Berners-Lee/Weaving/glossary.html

• In RDBMS terms, a Schema is a collection of tables, indexes, views, etc. in a database. Feature and RDBMS schemas do not correspond 1:1. A Feature Schema may be stored in different RDBMS schemas and an RDBMS schema might be composed of multiple logical schemas.
  fdo.osgeo.org/glossary.html

• An XML schema defines the structure of an XML document. An XML schema defines things such as which data elements and attributes can appear in a document; how the data elements relate to one another; whether an element is empty or can include text; which types of data are allowed for specific ...
  epa.gov/exchangenetwork/glossary.html