There are various synonyms available for the phrase "become stronger". They include; fortify, invigorate, strengthen, empower, enhance, toughen, reinforce, boost, energize, and harden. Fortify signifies making something strong and sturdy, while invigorate means to fill with energy and vitality. Strengthen indicates making something physically or mentally stronger, while empower indicates providing the means to become stronger. Enhance suggests adding value or improving something, while toughen signifies making something more resistant to harm. Reinforce denotes adding strength to something that is already strong, while boost implies helping something to become stronger. Energize denotes providing energy to something, while harden suggests making something more rigid and resistant.