Full-Text Search in SQL Server component and run full-text queries against character-based data in SQL Server tables.
Full-Text Search is an optional component of the SQL Server Database Engine. If you didn't select Full-Text Search when you installed SQL Server, run SQL Server Setup again to add it.
More information available on https://docs.microsoft.com/en-us/sql/relational-databases/search/full-text-search?view=sql-server-2017
How to add FTS feature to an Instance
Following document provides a step-by-step procedure for adding features to an instance of SQL Server.
Full-text search component can be selected from the available features list, when adding new features to the existing MSSQL server edition.
Availability of the Full-text search component depends on the SQL server edition (see the table below).