下级: low ranking, low level, underclass, subordinate...
召开: to convene (a conference or meeting), to convoke, to call together...
无形中: imperceptibly, virtually...
发育: to develop, to mature, growth, development, (sexually) mature...
内心: heart, innermost being, (math.) incenter...
词汇: vocabulary, list of words (e.g. for language teaching purposes), word...
漫游: to travel around, to roam, (mobile telephony) roaming...
