To solve the problem of finding the rank of the word "ZENITH" when all the letters are arranged in alphabetical order, we can follow these steps:
### Step-by-Step Solution:
1. **Identify the Letters in Alphabetical Order**:
The letters in the word "ZENITH" are Z, E, N, I, T, H. Arranging them in alphabetical order gives us:
- E, H, I, N, T, Z.
2. **Count Words Starting with Each Letter Before 'Z'**:
We need to count how many words can be formed starting with each letter that comes before 'Z':
- **Starting with E**: The remaining letters are H, I, N, T, Z. The number of arrangements is \(5! = 120\).
- **Starting with H**: The remaining letters are E, I, N, T, Z. The number of arrangements is \(5! = 120\).
- **Starting with I**: The remaining letters are E, H, N, T, Z. The number of arrangements is \(5! = 120\).
- **Starting with N**: The remaining letters are E, H, I, T, Z. The number of arrangements is \(5! = 120\).
- **Starting with T**: The remaining letters are E, H, I, N, Z. The number of arrangements is \(5! = 120\).
Adding these gives us:
\[
120 + 120 + 120 + 120 + 120 = 600.
\]
3. **Count Words Starting with 'Z'**:
Now we consider words that start with 'Z'. We need to look at the letters that follow 'Z' in alphabetical order:
- The remaining letters are E, H, I, N, T.
4. **Count Words Starting with 'ZE'**:
- Remaining letters: H, I, N, T. The number of arrangements is \(4! = 24\).
5. **Count Words Starting with 'ZH'**:
- Remaining letters: E, I, N, T. The number of arrangements is \(4! = 24\).
6. **Count Words Starting with 'ZI'**:
- Remaining letters: E, H, N, T. The number of arrangements is \(4! = 24\).
7. **Count Words Starting with 'ZN'**:
- Remaining letters: E, H, I, T. The number of arrangements is \(4! = 24\).
8. **Count Words Starting with 'ZT'**:
- Remaining letters: E, H, I, N. The number of arrangements is \(4! = 24\).
9. **Count Words Starting with 'ZEN'**:
- Remaining letters: H, I, T. The number of arrangements is \(3! = 6\).
10. **Count Words Starting with 'ZEH'**:
- Remaining letters: I, N, T. The number of arrangements is \(3! = 6\).
11. **Count Words Starting with 'ZEI'**:
- Remaining letters: H, N, T. The number of arrangements is \(3! = 6\).
12. **Count Words Starting with 'ZENI'**:
- Remaining letters: H, T. The number of arrangements is \(2! = 2\).
13. **Count Words Starting with 'ZENITH'**:
- This is the word we are interested in, so we stop here.
### Final Calculation of Rank:
Now, we sum all the counts:
\[
600 \text{ (from letters before Z)} + 24 + 24 + 24 + 24 + 24 + 6 + 6 + 6 + 2 + 1 \text{ (for ZENITH itself)} = 616.
\]
Thus, the rank of the word "ZENITH" is **616**.