Definition of 'Sector Breakdown'
The mix of sectors within a fund or portfolio, typically expressed as a percentage of the equities asset class. Sector designations vary slightly depending on the criteria used, but the most common equity sectors include:
Investopedia explains 'Sector Breakdown'
Sectors are a broader classification than industries, although some companies (especially more modern ones) can make a case for being "counted" in several different sectors. Companies within the same sector tend to have relatively high correlations in their rate of revenue and earnings growth, stock price performance, and earnings forecasts - especially over short- and medium-term time periods.
A diversified stock portfolio should hold stocks across most, if not all, sectors. Market weightings of sectors can be found by looking at the composition of a broad index like the S&P 500.