What is a prefix of standard?

There isn't a single, universally accepted prefix for "standard". However, depending on the context, these prefixes could be used:

General prefixes:

* Non- (non-standard) - indicating something that deviates from the norm

* Sub- (substandard) - indicating something that is below the accepted standard

* Super- (superstandard) - indicating something that exceeds the usual standard

* Pre- (pre-standard) - indicating something that exists before a standard is established

More specific prefixes:

* De- (de-standardize) - indicating a process of removing standardization

* Re- (re-standardize) - indicating a process of re-establishing a standard

* Co- (co-standard) - indicating a standard that is shared or agreed upon by multiple parties

The appropriate prefix will depend on the specific meaning you are trying to convey.