Let's solve the crossword puzzle step-by-step.

### Across Clues:
1. Something that does not happen on purpose. (10 letters) - **Accidental**
5. Something which is very unusual. (9 letters) - **Exceptional**
6. To suddenly go away. (3 letters) - **Run**
7. The doctor may prescribe this when you are poorly. (8 letters) - **Medicine**
8. Use a ruler to make sure your lines are... (7 letters) - **Straight**

### Down Clues:
2. You do a lot of this in science lessons. (9 letters) - **Experiment**
3. Put your important dates in one of these. (6 letters) - **Diary**
4. The second month of the year. (8 letters) - **February**

Now let's fill in the crossword:

#### Across:
1. **A C C I D E N T A L**
5. **E X C E P T I O N A L**
6. **R U N**
7. **M E D I C I N E**
8. **S T R A I G H T**

#### Down:
2. **E X P E R I M E N T**
3. **D I A R Y**
4. **F E B R U A R Y**

### Hidden Word:
The highlighted boxes spell out **CREATION**.

### Questions:
1. **What does the secret hidden word mean?**
   - Creation means the act of bringing something into existence.

2. **Write the secret hidden word in a sentence.**
   - The creation of the new software took several months of hard work.