Related Clues:

• Some of them are perfect
• Present and future, e.g.
• Verbal inflections
• Strains
• Past, present and future
• Will can change them
• Tightens (up)
• Past and present, for two
• Grammar topic
• Foreign language topic
• Grammar topics
• Present and future
• Grammarian's concern
• Freezes up
• Past and present