The best replacement for task is relationship.

The best alternatives to task are rated as following:
★★★★★  relationship
★★★  activity
★★★  project
★★★  thread
★  tasks
★  job
★  function
★  backgroundworker
★  goal
  event
  async
  responsibility
  duty
  engaged
  multitask
  skill
  project definition
  thread c#
  to do list

Your alternative for task is not listed? Suggest!
Speaking about task, one probably shouldn't forget about await.

Other search terms related to task and their ratings are:
★★★★★ await
You have in mind a companion for task and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of task in all years. Click on graph for more.
task
relationship
activity