WTA/ITF - Women Competitions
For more details you can look into
2015 WTA Official Rulebook (Internet Archive). Briefly summarized it says in the section XV. Age eligibility and player development that:
- Players under 14 cannot enter tournaments on WTA or ITF Women's Circuit.
- Above 14 players can play in Fed Cup.
- 14 years old player can play at 8 ITF Women's Circuit tournaments. (This limit is on the number of tournaments between her 14th and 15th birthday.)
- 15 years old player can play 10 tournaments (and WTA Finals or WTA Elite Trophy if she qualifies).
- 16 years old player can play 12 tournaments (and WTA Finals or WTA Elite Trophy if she qualifies).
- 17 years old player can play 16 tournaments (and WTA Finals or WTA Elite Trophy if she qualifies).
- For players that reached 18 years there is no limit on the number of professional tournaments.
ITF - Junior Competitions
There are also limits on the number of junior tournaments a player may enter. Again, for more details see 2014 Junior Circuit Regulations (Internet Archive).
I will reproduce here the table from that document (Appendix G: ITF junior circuit age eligibility rule) which gives an overview.
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| Age | Number of Tournaments permitted |
| 18 | Unrestricted |
| 17 | Unrestricted |
| 16 | 25 |
| 15 | 16 (and 4 additional tournaments for players in Top 20) |
| 14 | 14 (and 4 additional tournaments for players in Top 20) |
| 13 | 10 (and 4 additional tournaments for players in Top 50) |
| 11/12 | 0 |
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