The amino acids which human body cannot synthesise are called ............ amino acid.

Explanation

**Step-by-Step Solution:**

1. **Understanding Amino Acids**: Amino acids are organic compounds that serve as the building blocks of proteins. They play a crucial role in various biological processes in the human body.

2. **Classification of Amino Acids**: Amino acids are classified into three categories:
- **Essential Amino Acids**: These are amino acids that the human body cannot synthesize on its own. Therefore, they must be obtained through dietary sources.
- **Non-Essential Amino Acids**: These amino acids can be synthesized by the body, meaning that even if they are not consumed through food, the body can produce them.
- **Conditional Amino Acids**: These amino acids are usually not essential but may become essential in times of illness or stress.
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