subintroduce /sub-in-trō-dūsˈ/

To bring in surreptitiously or subtly

• letter-heading
• letterheads
• lettering
• letterings
• letterless
• letter missive
• lettern
• letter of attorney
• letter of comfort
• letter of credit
• letter of indication
• letter-of-marque
• letter of peace
• letter-perfect
• letterpress
• letterpresses
• letter quality
• letter-quality
• letters
• letters credential
• letterset
• lettersets
• letters of administration
• letters of comfort
• letters of credence