Hello ASMAE.KAJJOUT,
Thank you for posting in Q&A forum.
Yes, you can install Microsoft 365 on up to 5 devices with a single subscription. This includes devices such as PCs, Macs, tablets, and smartphones. So, you can definitely install Word, Excel, and other Microsoft 365 tools on 4 different devices while still having one installation slot remaining.
Please refer to the following link: https://support.microsoft.com/en-us/office/how-sign-in-works-in-microsoft-365-1d646e83-1585-4278-8daf-d4a2cc0905e0#ID0EBD=signinmsa
Please don't hesitate to reach out to us if you have any further queries.
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