.ren FAQ

In accordance with ICANN schedule of reserved names the following are restricted: “EXAMPLE” shall be reserved at the second level and at all other levels within the TLD at which Registry Operator makes registrations.
Two-character labels: All two-character labels shall be initially reserved. The reservation of a two character label string may be released to the extent that Registry Operator reaches agreement with the government and country-code manager. The Registry Operator may also propose release of these reservations based on its implementation of measures to avoid confusion with the corresponding country codes.
Tagged Domain Names: Labels may only include hyphens in the third and fourth position if they represent valid internationalized domain names in their ASCII encoding (for example "xn--ndk061n").
Second-Level Reservations for Registry Operations: The following names are reserved for use in connection with the operation of the registry for the TLD. Registry Operator may use them, but upon conclusion of Registry Operator's designation as operator of the registry for the TLD they shall be transferred as specified by ICANN: NIC, WWW, IRIS and WHOIS.
Country and Territory Names: The country and territory names contained in the following internationally recognized lists shall be initially reserved at the second level and at all other levels within the TLD at which the Registry Operator provides for registrations.

Top Level Reserved Names: AFRINIC, IANA-SERVERS, NRO, ALAC, ICANN, RFC-EDITOR, APNIC, IESG, RIPE, ARIN, IETF, ROOT-SERVERS, ASO, INTERNIC, RSSAC, CCNSO, INVALID, SSAC, EXAMPLE, IRTF, TEST, GAC, ISTF, TLD, GNSO, LACNIC, WHOIS, GTLD-SERVERS, LOCAL, WWW, IAB, LOCALHOST, IANA, NIC, All International Olympic Committee names, All International Red Cross and Red Crescent Movement names.