Definition first
Capture what the denominator and numerator are so that periods and segments remain fairly similar.
Glossary
Conversion Rate
Conversion Rate is the percentage of visitors, sessions, or other chosen units that complete a desired action, such as an order.
Search context
Searching visitors may have different buying intent than non-searching visitors; therefore, consciously compare segments.
Not isolated
Combine conversion rate with search volume, CTR, zero-result searches and order value to avoid wrong conclusions.
Influences
Season, campaigns, assortment and traffic can change conversion rate without search itself being customized.