• Basic forms
• 切る — to cut / to sever / base form
• 切ります — (I) cut / masu form
• 切った — cut (past) / ta form
• 切って — cut (and …); please cut / te-form
• 切らない — do not cut / negative form
• 切れば — if (someone) cuts / conditional
• 切れ・切りなさい — cut! / imperative
• Other common forms
• 切りたい — want to cut / 〜たい form
• 切れる — can cut; be sharp; be severed / potential / intransitive sense
• 切れた — was severed / broke / intransitive past
• 切れない — cannot cut; won’t cut through / negative potential
• More
• 切ろう — let’s cut / 〜よう form
• 切らなかった — didn’t cut / past negative
• 切っている — is cutting; is in the process of cutting / progressive

切る（きる） is a godan verb ending in る. Stem alternates as る → り → っ, forming 切る・切ります・切って・切った. Note: 切れる is also widely used as an intransitive form meaning “to snap / to break / to be sharp.”