• Basic forms
• 防ぐ — to prevent; to defend against / base form
• 防ぎます — prevent; defend against / masu form
• 防いだ — prevented; defended against / ta form
• 防いで — prevent and … / te form
• 防がない — do not prevent / negative
• 防げば — if (one) prevents / conditional
• 防げ — prevent! / imperative
• Common expressions
• 事故を防ぐ — prevent an accident
• 被害を防ぐ — prevent damage
• 病気を防ぐ — prevent illness
• More
• 防ごう — let’s prevent / volitional
• 防げない — cannot prevent / negative potential

防ぐ（ふせぐ） is a godan verb. It means to actively stop something harmful or undesirable before it happens, and is commonly used with abstract nouns such as accidents, damage, illness, or danger.