Stock trading and social media share some similar traits. "Views," for instance, on a YouTube video and "likes" on Instagram and Facebook posts are basic gauges of demand. They tell advertisers and others just how many people are attracted or paying attention to a particular post.

The similar measure in stock trading is trading volume. Volume, simply put, means the number of shares trading hands — bought or sold. This can be for a day or for a week, or even a month. And it can be for an index or an entire stock exchange (NYSE and Nasdaq daily volumes are key to IBD's daily Big Picture analysis).

It is also a crucial measure for an individual stock. And for growth stocks in particular, as investors assess the buying demand behind a stock's base building and breakouts.

There are three instances in which volume is a critical measure: daily dollar volume, base building and breakouts.

Stock Trading: Volume Basics

First things first: Most stock chart services gauge volume in bar charts, running across the bottom of the typical stock price screen. This is true for IBD's stock charts at investors.com. The chart across the bottom of the screen shows blue bars for days when the stock closes higher, reddish pink bars when the stock takes a loss.

The right side of the charts shows stock volume levels, either in thousands (K) or millions (M) of shares. The horizontal red line running about midday across the screen plots the average for a stock's trading volume over the 50 most recent sessions.

Up days (blue bars) that rise above that 50-day moving average are bullish signs. Down days (red bars) in above-average trade signal at least one institutional investor is paring its position in the stock.

1. Daily Stock Trading Dollar Volume

Daily dollar volume is a way to confirm that a potential leading stock has sufficient liquidity to attract the size and number of large-scale investors that typically drive serious stock advances. Go to IBD's Stock Quote function and find the 50-day average volume measure under the Stock Data listing.

Multiply the average daily volume by the stock's price. You want the sum to be, at a minimum, in the $20 million to $25 million range. A stock that trades around $50 per share, for example, would need to trade an average of at least 400,000 shares per day. A stock that trades at $125, on the other hand, would only need an average volume of 160,000 shares.

2. Volume In Bases

When a stock is building a base, on a daily chart, you want to see more up days in above-average volume, fewer high-volume down days — especially as the stock climbs the right side of the pattern, such as the cup with handle or the flat base. This is also true for weekly volume on a weekly chart.

A high-volume day and/or week right around the low point of a cup base is a good sign. This can be either a down day, a shakeout of sellers dumping their last shares; or an up day, a new fund grabbing an initial position at what it reads as a nadir in the consolidation.

Later in a base, volume that fades to below average as a stock chart builds a handle is a good sign. This signals all would-be sellers have been shaken out during the basing process.

3. Breakout Volume

The make-or-break volume measure is breakout volume. A growth stock needs to trade in volume that is 40% above its 50-day average volume as it passes a proper buy point in order to mark a valid breakout. You can find the necessary information using the Stock Checkup function at investors.com. Near the top of the page, on the left hand side, the stock charts provide a "Volume % Change" reading. So does Stocks On The Move, a great stock list for discovering new breakouts.

You would like a growth stock to finish a breakout session with that volume % change number at least 40% for the entire day. Sometimes trading volume can be comparatively weak on the day of a breakout, but will surge sometime over the next few sessions — driving the stock higher and confirming the breakout.