• Basic forms
• 足りる — to be enough; to suffice / base form
• 足ります — (it) is enough / masu form
• 足りた — was enough / ta form
• 足りて — be enough (and …) / te-form
• 足りない — not enough; lacking / negative form
• 足りれば — if it is enough / conditional
• 足りろ — be enough! / imperative
• Other common forms
• 足りなかった — wasn’t enough / past negative
• 足りている — is sufficient; is enough / progressive
• 足りていない — is not sufficient / negative progressive

足りる is an ichidan (1-dan) verb. Drop る and add endings like ます, た, て, ない — as in お金が足りない (“there isn’t enough money”) or 時間が足りている (“we have enough time”).

• Basic forms
• 足す — to add; to top up / base form
• 足します — I add / I will add / masu form
• 足した — added / ta form
• 足して — add (and …) / te-form
• 足さない — do not add / negative form
• 足せば — if (someone) adds / conditional
• 足せ — add it! / imperative
• Other common forms
• 足さなかった — did not add / past negative
• 足している — is adding; is topping up / progressive
• 足していない — is not adding / negative progressive

足す is a godan (5-dan) verb meaning “to add” or “to supplement.” You’ll see it in phrases like 砂糖を足す (add sugar) or 時間を足す (add more time).