The US-based index, which is home to some of the world’s best known technology and internet companies, was hit by a sell-off during Thursday’s trading session. It fell 1.6% over the course of the day, finishing at 6,528 points.

Professional investors are alarmed because yesterday’s trading session saw the Nasdaq move 20% lower since it reached its previous high at the end of August. A bear market is defined as a 20% drop from a high point. Fortunately, the index recovered some of its losses towards the end of the day – and finished 19.7% lower than its previous record.

The US has three major indices that investors watch closely: the Nasdaq, the S&P 500 and the Dow Jones Industrial Average. The latter three are around 15% lower in comparison to their previous respective highs.

On Friday morning, the FTSE 100 index was trading 0.5% lower at 6,682 points.