Lifecycle ceremonies and ordination
In one sense, ceremonies marking birth, adulthood, or marriage are seen as purely worldly activities, not relevant to the spiritual pursuit, and so monastics are rarely involved. Having said that, there are often blessings from monks for a new baby, new house or wedding (maybe separate from any civil ceremony), and in some Buddhist groups religious marriage ceremonies do exist, including for same-sex partners, even before civil provision. As this article is being written in July 2020, Thailand looks likely to be the first Buddhist-majority country to legalise ‘same sex unions’.
Funerals are different, as relevant to reflecting on the central concerns of Buddhism with suffering and death. Funerals are conducted by monks or other Buddhist clergy in many Buddhist cultures. In Japan it is something of a Buddhist speciality (‘born Shinto, die Buddhist’). The dead are clothed as if for ordination, and memorial tablets are kept in Buddhist temples.
There are ceremonies for the ordination of novices, and for full ordination as a monk (or nun, where this exists). In some countries, such as Sri Lanka and Tibet, boys can become novice monks as children, and this was a way of gaining an education before state provision of schools, later taking full ordination or returning to lay life. In other countries, for example in Thailand, periods of temporary ordination for men for perhaps a month or so are common as a transition to adulthood, or before getting married.