TA & charts, page-784

Volume shows how much conviction investors have with a trend. Low volumes and a price drop may indicate little conviction in that down-trend.

High volumes on a price drop may indicate high conviction in a down-trend.

High volume on a price rise may indicate high conviction in an up-trend. Low volume on price-rise may indicate little conviction in the up-trend.

when volume is low, price is easier to manipulate. It's always good to keep an eye on all your tickers respective volumes and what the volume generally averages. Also good to look at the parcel sizes that are changing hands

This is not definitive and doesn't always ring true, hence the use of my word 'may'....