(Oxford Music Online)

In general a (late) baroque fugue can be recognized by:

• imitation between voices/parts
• the use of a theme or subject which is presented by all participating voices
• often answered in a fifth
• this answer can be unchanged (real answer) or slightly changed for harmonic reasons (tonal answer).
• often there are theme-entry groups
• theme-entry groups are often separated by episodes (sections without theme-entries)
• the use of contrapuntal techniques, such as stretto, the use of a counter-subject
• the use of a pedal point towards to end of the fugue
• ...