The word "invig" refers to the action of giving strength, vitality, or energy to someone or something. If you're looking for synonyms to use in your writing piece, you can use words such as "strengthen," "refresh," "revitalize," "renew," "enliven," "recharge," "revive," "boost," "energize," "animate," "stimulate," "fortify," "regenerate," "vivify," "awaken," and "sustain." All of these words convey the idea of invigorating or restoring something back to its original state of vigor, strength, and vitality. Using synonyms can add variety and depth to your writing, allowing you to better cater to your audience and convey your message more effectively.