TO RETAIN, practice. To engage the services of an attorney or counsellor to manage a cause, at which time it is usual to give him a fee, called the retaining fee. The act by which the attorney is authorized to act in the case is called a retainer.
One explanation for the difference in the levels of catechins found in this study and others is the type of samples used. In comparative studies, leaves of Camellia sinensis 4 Discussion Table 1. Levels of catechins and caffeine in tea bags, extract, and ready-to-drink green tea.
Generally, no. But that all depends on the plant too. Most herbal teas do not contain caffeine. However, you do get a few outliers here and there--- for example, yerba mate and guarana do have a caffeine content.