Related Clues:

• Part of speech
• Communicate by hand
• Self-identifying word
• Parsing choice
• Proper word, at times
• It may be a proper subject
• Affix an X, maybe
• Common word?
• Make a contract legal
• Make it official
• Hook, line or sinker
• Sentence part
• Verb subject
• What a catcher puts down
• It's subject to modification