• Basic forms
• 研ぐ — to sharpen; to grind; to polish / base form
• 研ぎます — (I) sharpen / masu form
• 研いだ — sharpened / ta form
• 研いで — sharpen (and…); please sharpen / te-form
• 研がない — do not sharpen / negative form
• 研げば — if (you) sharpen / conditional
• 研げ — sharpen! / imperative
• Other common forms
• 研ぎたい — want to sharpen / 〜たい form
• 研げる — can sharpen / potential
• 研げなかった — couldn’t sharpen / negative potential
• More
• 包丁を研ごう — let’s sharpen the kitchen knife / 〜よう form
• 研いでいる — is sharpening; is grinding / progressive

研ぐ（とぐ） is a godan verb ending in ぐ. Stem alternates as ぐ → ぎ → いだ, giving forms like 研ぎます・研いで・研いだ. Often used for sharpening knives, polishing rice, or grinding materials.