Adult

Adult is a life stage existing in The Sims, The Sims 2, The Sims 3 and The Sims 4. In The Sims 2, it is normally the longest life stage in a Sim's life; in The Sims 3, it is the same length as the young adult stage. In The Sims it is the last life stage before death, while in The Sims 2, The Sims 3, and The Sims 4 it is followed by the elder life stage. In The Sims 2, it is the default age for Sims created in CAS.

In this stage, Sims can take up full-time careers, get married, give birth and adopt children. In The Sims, they are the only Sims who can prepare food. Consequently, it is fairly difficult for a household to function without adults.

Adult Sims can use most of the objects in the game and perform the most interactions with other Sims.

The Sims
In The Sims, being an adult is permanent and children do not become adults without spells, mods, or third-party tools. While adult Sims can die if something kills them, they never age, so they have indefinite lifespans. It is the main lifespan of the Sims in this game.

The Sims 2
In The Sims 2, the adult stage is the longest and most important life stage. It is preceded by the teen life stage, or the optional young adult stage if The Sims 2: University is installed. It is the only life stage in which a Sim can get pregnant and get a full-time job.

The Sims 3
In The Sims 3, the adult stage is no longer the default age when entering Create a Sim, having been replaced in this role by a new version of the young adult stage. Adults in The Sims 3 instead represent middle-aged Sims, and are approximately between 40 years old and retirement age. They will gain a few wrinkles upon aging up from young adults, but not to the same extent as Sims in the elder stage. They also can have age details, in CAS.

Gameplay-wise, there are few noticeable differences between an adult and a young adult; they can still get married, join careers and have children, and will not gain any further traits. However, the likelihood of a female adult Sim successfully becoming pregnant when attempting the Try for Baby interaction is somewhat lower than it is for a young adult Sim.

If The Sims 3: Generations is installed, adults are slightly more distinct from young adults. Depending on their actions and achievements (or lack thereof) as a young adult, a Sim may experience a midlife crisis at the beginning of the adult stage. This causes the Sim to gain a special moodlet for a number of days equal to 25% of the lifespan (if this results in a decimal value, it is rounded up), which will cause them to roll midlife crisis-related wishes distinguished by a red background. If the player promises and fulfills the Sim's crisis wishes, the moodlet will become a positive one, but if no wishes are fulfilled the moodlet will become negative. Any crisis wishes promised by the player cannot be canceled until the moodlet expires, though a midlife crisis can be ended early by going to the hospital and selecting the new "Get Therapy" option.