Cutting insert, cutting tool, and method for manufacturing machined product

A cutting insert, comprising:

• an upper surface;
• a lower surface located on a side opposite to the upper surface;
• a front end surface located between the upper surface and the lower surface;
• a first lateral surface adjacent to the upper surface and the front end surface;
• a second lateral surface which is located on a side opposite to the first lateral surface and is adjacent to the upper surface and the front end surface;
• a front cutting edge located on an intersection of the upper surface and the front end surface;
• a first lateral cutting edge located on an intersection of the upper surface and the first lateral surface;
• and
• a second lateral cutting edge located on an intersection of the upper surface and the second lateral surface,
• wherein
• the upper surface comprises
• a front rake surface which is located along the front cutting edge and is closer to the lower surface as going away from the front cutting edge,
• a first lateral rake surface which is located along the first lateral cutting edge and is closer to the lower surface as going away from the first lateral cutting edge, and
• a breaker protrusion which is located further away from the first lateral cutting edge than the first lateral rake surface and is extended along the first lateral rake surface,
• the first lateral cutting edge comprises an inclined part which is closer to the lower surface as going away from the front cutting edge, and
• the breaker protrusion comprises, in a side view from a side of the first lateral surface,
• a first region located further away from the lower surface than the inclined part,
• a second region which is located closer to the front cutting edge than the first region and is located closer to the lower surface than the inclined part, and
• a third region which is located further away from the front cutting edge than the first region and is located closer to the lower surface than the inclined part.