• Basic forms
• 想う — to think; to feel; to hold in one’s heart / base form
• 想います — (I) think; feel / masu form
• 想った — thought; felt / ta form
• 想って — think/feel and … / te-form
• 想わない — do not think / do not feel / negative form
• 想えば — if (you) think / feel / conditional
• 想え — think!; feel! / imperative
• Other common forms
• 想いたい — want to think / want to feel / 〜たい form
• 想える — can think; can feel / potential
• 想えた — was able to think / realize / past potential
• 想えない — cannot think; cannot feel / negative potential
• More
• あなたを想う — to think of you; to hold you in my thoughts
• 深く想っている — thinking deeply; holding strong feelings
• 想われている — to be thought of / cherished / passive

想う（おもう） is a godan verb. It often carries a more emotional or reflective nuance than 思う — used for heartfelt thoughts, memories, and personal feelings.