Categorize the following three words.
Happiness, Energy, Rainbow
Category: Abstract Concepts/Nouns.

1. Happiness - Emotion/Feeling
2. Energy - Physical/Scientific Concept
3. Rainbow - Natural Phenomenon.
Complete the following task based on the instruction and optional input provided.### Instruction:
Categorize the following three words.

### Input:
Happiness, Energy, Rainbow

### Output:
Category: Abstract Concepts/Nouns.

1. Happiness - Emotion/Feeling
2. Energy - Physical/Scientific Concept
3. Rainbow - Natural Phenomenon.