One portion of a larger amount of money that is handed over or dealt with separately — the first tranche of a loan, a tranche of shares, a tranche of aid. The key idea is that the whole sum was deliberately cut into pieces and released piece by piece, usually over time or on conditions: the government pays the second tranche once the targets are met. It comes from French for 'a slice', and English kept the French sound and spelling, which is why it feels formal. It lives in business news, banking, and government reports. In finance it has a tighter meaning: when a big pool of loans is packaged and sold, the tranches are the layers with different levels of risk and return — the senior tranche gets paid first, the lowest tranche absorbs the losses first. That is the sense you met in the 2008 financial crisis coverage. Journalists have also stretched it beyond money to mean any batch released in stages — a tranche of documents, a tranche of new members.