| 41. | internal combustion engine |
| 内燃机
|
| 42. | internal [domestic] commerce |
| 国内贸易
|
| 43. | external [ internal ] debt |
| 外[内]债
|
| 44. | internal [inside] diameter |
| 内径
|
| 45. | endanger internal security |
| 危及国内治安
|
| 46. | a female [an internal ] screw |
| 阴螺旋，内螺旋
|
| 47. | internal strife |
| 内讧
|
| 48. | external [ internal ] storage |
| 外[内]存储器
|
| 49. | after terrific mental [ internal ] struggles |
| 在激烈的思想斗争以后
|
| 50. | an internal student |
| 校内学生（大学中在校注册上课并参加学位考试的学生）
|