A Mormon mission is a period of volunteer service, usually ranging from six to 24 months, when Church members devote themselves part-time or full-time to proselytizing, humanitarian assistance, or other service. Missionaries of the Church of Jesus Christ of Latter-day Saints (LDS Church) are volunteer representatives of the church who engage in various activities such as proselytizing, church service, humanitarian aid, and community service. Missionaries may be male (Elder Missionaries) or female (Sister Missionaries) and may serve on a full- or part-time basis, depending on the assignment. They are organized geographically into missions, which could be any one of the 411 missions organized worldwide. Most full-time LDS missionaries are single young men and women in their late teens and early twenties and older couples no longer with children in their home. Missionaries are often assigned to serve far from their homes, including in other countries. Many missionaries learn a new language at a missionary training center (MTC) as part of their assignment. Missions typically last two years for males, 18 months for females, and one to three years for older couples. All Mormon missionaries serve voluntarily and do not receive a salary for their work; they typically finance their missions themselves or with the help of their families and congregations.