To simplify the expression \( 1 + i + \frac{1}{3} + \frac{\sqrt{3}}{3}i \), we start by combining like terms, specifically the real and imaginary parts.
Combine the real parts: \[ 1 + \frac{1}{3} = \frac{3}{3} + \frac{1}{3} = \frac{4}{3} \]
Combine the imaginary parts: \[ i + \frac{\sqrt{3}}{3}i = \left(1 + \frac{\sqrt{3}}{3}\right)i = \left(\frac{3}{3} + \frac{\sqrt{3}}{3}\right)i = \frac{3 + \sqrt{3}}{3}i \]
Now we can combine the two parts:
\[ 1 + i + \frac{1}{3} + \frac{\sqrt{3}}{3}i = \frac{4}{3} + \frac{3 + \sqrt{3}}{3}i \]
So the final simplified expression is:
\[ \frac{4}{3} + \frac{3 + \sqrt{3}}{3}i \]