The default is a state that exists unless it is altered.
Many grammatical systems have defaults; for example default polarity is affirmative.
A longer list:
- Aspect - simple aspect (i.e. lack of aspect)
- Grammatical gender - neuter
- Modality - amodality (lack of modality)
- Mood - declarative mood
- Grammatical number - Singular
- Grammatical person - third person
- Polarity - affirmative
- Tense - present tense
- verb form - base form
- Grammatical voice - active voice