1N-UNCOUNT [with poss]（君主、帝王的）登基，即位；（国家统治者的）就职，就任Accession is the act of taking up a position as the ruler of a country. （君主、帝王的）登基，即位；（国家统治者的）就职，就任 [formal]
...the 50th anniversary of the Queen's accession to the throne. [+ to]
女王登基50周年庆典
2N-UNCOUNT [oft with poss, Nto n]正式加入 A country's accession to a group of countries or to an association is its joining that group of countries or association. 正式加入 [formal]
...Namibia's accession to the Lome convention.
纳米比亚正式加入《洛美协定》
...a ballot over the issue of Kashmir's accession to India.