The Sahara Is Not an Erg—It Contains Ergs

No. An erg is a specific landform: a vast sea of wind-blown sand dunes (>125 km²). The Sahara Desert is a continental-scale desert comprising multiple landscapes:

• Ergs (sand seas): Grand Erg Oriental, Grand Erg Occidental, Erg Chech, etc. — ~20% of Sahara.
• Hamadas: Rocky plateaus (bare bedrock).
• Regs: Gravel/stony plains (desert pavement).
• Wadis: Dry river channels.
• Mountains: Tibesti, Ahaggar, Aïr massifs.
• Depressions: Qattara, Siwa, chotts (salt flats).
• Oases: Groundwater-fed agriculture.

So the Sahara contains ergs—it is not one.