A Greek trireme. A Trireme is an ancient oar-driven warship powered by about 170 oars men. It was long and slender, had three tiers of oars and one sail. On the bow was a battering ram that was used to destroy enemy ships. The tip of the ram was made of bronze and could easily slice through the side of a wooden ship.
When you buy 1,000 shares of Ford at $14 and your broker charges you a $10 commission, your cost basis is $14,010 for those shares. That transaction is given a unique tax lot ID so you and the IRS can track those shares separately from other Ford stock you might buy later.
The ETF tracking error is the difference between the returns of the ETF and its reference index or asset. A non-zero tracking error therefore represents a failure to replicate the reference as stated in the ETF prospectus. The tracking error is computed based on the prevailing price of the ETF and its reference.