Analog Signals: An analog signal exists throughout a continuous interval of time and/or takes on a continuous range of values.
Batteries: A battery is a limited source of energy. This energy is stored in chemical form is readily available for conversion into electrical energy.
Bias: A bias (or bias voltage) is the voltage needed by device for proper function. Two examples include (1) the common-emitter BJT configuration where VCC and RC provide a bias voltage to the collector that allows for the typical set of IV responses provided in the datasheets and (2) an electret condenser microphone that requires a a resistor (typically around 1-10 kOhm) to tie the drain of an internal JFET preamp to a voltage source (typically 3-9 V).
...Voltage Amplifier: Although the raw look at the BJT is based upon the amplification of a current, the basic configuration also leads quickly to analysis as a voltage amplifier (think "guitar amp"!).
...Datasheet: You can look up a BJT's characteristics online.
Fourier Series: Any practical periodic voltage signal can be represented as a sum of sinusoids.
Graphs: Graphs should have a title or caption and properly labeled axes.
Huffman: David A. Huffman was an electrical engineering and a pioneer of computer science who remains well-known for his 1952 paper describing a sometimes-optimal compression algorithm. Explore More! at Wikipedia.org.