Adverbs of frequency are used to express how often an activity is done. They include always, usually, normally/generally, often/frequently, sometimes, occasionally, seldom, hardly ever/rarely, and never. Frequency adverbs go before main verbs except with forms of "to be", where they follow the verb. Exceptions allow usually, normally, often, frequently, sometimes, and occasionally to begin sentences, while always, seldom, rarely, hardly, ever, and never cannot. Hardly ever and never are used with positive verbs, and ever is used in questions and negative statements.