Relative delays

delay Wait_Time;

The Ravenscar profile forbids the use of the relative delay statement:

pragma Restrictions (No_Relative_Delay)

This language feature is only available from Ada 2005 on.

Absolute delays

delay until Next_Time;

Delay alternative

Selective accept:

select
   when Cond =>
      accept_statement
      statements
or
  delay_alternative
end select;

Timed entry call

select
   entry_call_alternative
or
   delay_alternative
end select;

Asynchronous transfer of control

select
   delay until Abort_Time;
   statements
then abort
   abortable_part
end select;

Wikibook

• Ada Programming
• Ada Programming/Keywords
• Ada Programming/Tasking
• Ada Programming/Pragmas/Restrictions/No Relative Delay

Ada Reference Manual

• 2.9 Reserved Words (Annotated)
• Annex P (informative) Syntax Summary (Annotated)

• 9.6 Delay Statements, Duration, and Time (Annotated)

• 9.7 Select Statements (Annotated)
• 9.7.1 Selective Accept (Annotated)
• 9.7.2 Timed Entry Calls (Annotated)
• 9.7.4 Asynchronous Transfer of Control (Annotated)

Ada Quality and Style Guide

• 3.1.3 Capitalization

• 6.1.7 Delay Statements