Note: This release is in preview. Features described here don’t become generally available until the latest general availability date that Salesforce announces for this release. Before then, and where features are noted as beta, pilot, or developer preview, we can’t guarantee general availability within any particular time frame or at all. Make your purchase decisions only on the basis of generally available products and features.

Reserved Keywords

These words can be used only as keywords.

Table 1. Reserved Keywords
abstract activate and any array as asc autonomous begin bigdecimal blob boolean break bulk by byte case cast catch char class collect commit const continue currency date datetime decimal default delete desc do double else end enum exception exit export extends	false final finally float for from global goto group having hint if implements import in inner insert instanceof int integer interface into join like limit list long loop map merge new not null nulls number object of on or outer override	package parallel pragma private protected public retrieve return rollback select set short sObject sort static string super switch synchronized system testmethod then this throw time transaction trigger true try undelete update upsert using virtual void webservice when where while

These words are special types of keywords that aren't reserved words and can be used as identifiers.

after
before
count
excludes
first
includes
last
order
sharing
with

Apex Developer Guide

Reserved Keywords