What does "schema" mean? In a relational model, 


a schema is something which specifies the name and data type of each field.
The word "schema" is also used in "conceptual schema", "physical schema" and "external schema". 


What do "schema" mean separately in the above two cases? Are they
related?

Are they related to the "schema" in cognitive psychology?
Is "schema" used in other areas of computer science, such as
artificial intelligence, programming languages, ...?
What does "schema" mean in computer science besides database?


Thanks!
1. **What is Schema**-  In a relational database, the schema defines the tables, the fields in each table, and the relationships between fields and tables.

Yes, They are related to these 3 words,  "conceptual schema", "physical schema" and "external schema". 


External schema for user views
Conceptual schema integrates external schemata
Internal schema that defines physical storage structures


No, It has no relation with "schema" in cognitive psychology

2. Yes, Schema used in other area also like in- 

Programming &amp; Algorithms -XML Schema , Schema (genetic algorithms) 
Science- Body Schema, Image Schema 
Mathematics- Axiom Schema (related to Mathematical Logic) 

3.  Refer above point 1 &amp; 2